Tyranids really were hurting in 5th edition to the point they had one major build - lots of T6. There were lots of variations around this but the core was generally Tervigons + Hive Guard, as many T6 MCs as could be fit in and whatever support (i.e. Genestealers, more little gribblies like Hormagaunts, Termagants, etc. Raveners, Tyranid Primes, etc.). The issue generally was lots and lots of high strength, low AP shooting could deal with the mass T6 over an average game and vehicles in general posed a problem Tyranids, particularly in combat. Let's see how this list transfers to 6th...
Now we've already looked at how 6th impacts Tyranids as whole and all in all, things are pretty good. They gained a lot really but they were so far behind some armies (which gained themselves universally due to one thing: Allies) they still really haven't caught up. They are much improved but are they on the same playing field? Yes & no - again, they'll have terrible match-ups and this is where we get an issue with massing T6. However, the issue of being able to deal with both infantry and vehicles is largely irrelevant now as vehicles are less likely to laugh off damage with skewed dice or giggle at the scrabblings of Monstrous Creatures in combat. Flyers though... Anyway, let's look at some quick fire gains and losses for the T6'R'Us build...
- Hive Guard were the golden standard of being awesome before. They got better. Point a full unit at anything AV12 or less and it dies. Chuck in Old Adversary to increase this probability and then point them at AV13 and likely watch heavy damage unfold there, too.
- Old Adversary affects shooting & combat now. It's not as good in terms of re-rolling all misses but re-rolling all 1's is very nice and still an excellent buff to have.
- Tanks in general are easier for Tyranids to handle due to Hull Points and AP - not being an issue. This means the mass of S6 weapons Tyranids have (like MC Devs) are actually useful beyond simple suppression.
- Hitting vehicles on 3's at worst in combat is also huge and not just for MCs but anything which can mass lots of attacks which can damage armor (i.e. S4 on AV10, Gargs, Rending, etc.) can quickly drop low AV vehicles. You're still hitting vehicles before the guys inside though but it's better than not getting to kill anything and the tank driving away.
- Random Charge Length is decent for both the big and little guys. The big guys generally don't care about Overwatch - they have lots of Wounds and high Toughness values anyway and the little guys have lots of little guys covering their backs to make up for the occasional losses. It can reduce your charge range for the little guys but they make such good tarpits which stop shooting at your big guys that attempting to launch longer charges can be worth the extra death or two. Assaulting into cover still sucks ass though.
- Fearless no longer has No Retreat wounds in close combat meaning your little guys are great tarpits and combined assaults are a much better prospect than before. Synapse also becomes more important as Fearless is better.
- Flying Monstrous Creatures...well. They are both good and bad. Good because they bring more mobility to the table and extra damage from Vector Strikes but this damage doesn't really scare flyers because...it's S6. They're also not that hard to take down with the Grounding effect and Harpies are still pretty expensive and only T5.
- The Tyrannofex has lost a lot of its utility - two S10 shots isn't as scary anymore since rate of fire is much more important. It still brings all the usual MC goodness and can provide cover pretty damn easily to other MCs but it's still very expensive and lost some of what it had previously.
- Speaking of cover - much easier to get for MCs but has gone down in terms how effective it is which is an issue. You could pretty reliably get a 4+ cover save in 5th edition early game so this is sort of a reduction. Having FNP work against AP2 or better weapons can mitigate this but you're still losing out on the AP3/4 stuff like Missile Launchers and Autocannons.
- Psychic powers are now much more readily available whilst actively benefiting the army. Tyrants, Zoanthropes, Tervigons & Broodlords can all swap out powers for some BYB psychic disciplines and although it's not recommended all the time (ahem, Tervigons), you can get some nice new abilities here.
- Flyers are a royal bitch. Tyranids basically replaced their inability to deal with mass vehicles with an inability to deal with a single flyer. There's minimal twin-linkage available for the good anti-tank options to shoot down flyers (outside of MC Devourers) and no flyers of their own. There are other ways to deal with them such as psychic powers or spreading out lots of little guys all over the place so they can't land but there's no *punch to the face* answer that other armies can bring.
What this all indicates is...less is more here and there's one major reason for this - cover reduction. You're looking at taking nearly 20% more wounds from Missile Launchers (or anything which denies you your 3+ save but allowed FNP in 5th) and 6% from Autocannons (or anything which allows you your 3+ save and FNP). This is offset by a 5.5% increase in wounds saved from Lascannons (or anything which denies you your 3+ save and didn't allow FNP in 5th) and whilst these type of weapons may become more popular, missile launchers, autocannons and the like aren't going to disappear in any significant way. This means massing T6 isn't as viable as it was before but certain units, like Hive Guard and Tervigons, are still excellent and almost necessary parts of the Tyranid arsenal. And since they are the core of the T6'R'Us army list, it can be transferred in some way to 6th edition.
So let's look at the template:
3x Hive Guard
3x Hive Guard
Tervigon w/Catalyst, Adrenal Glands, Toxin Sacs
Tervigon w/Catalyst, Adrenal Glands, Toxin Sacs
15x Termagants
15x Termagants
Carnifex w/2x twin-linked MC Devourers
Carnifex w/2x twin-linked MC Devourers
Totals: 1220 points
Lots and lots of points to work with which is a shame because Allies could really come in handy here. The lack of Allies hurts when we compare Tyranids to other armies but at least we have lots of points to play with here. Since we're trying to keep with the T6'R'Us comment I made sure we had a lot of T6 wounds with the Carnifexes added in. Perhaps not the best bet for Tyranids overall but they do add extra anti-tank through pure Hull Point removal, extra MCs to throw into combat and one of the few semi-decent answers to flyers in the Tyranid book.
We've got two squads of Hive Guard to cover our main anti-tank at range with a 3rd Elite slot open for more Hive Guard or Zoanthropes if you want to grab some psychic flexibility. The Termagant squads are bigger to make better tarpits - you cannot rely on your Tervigons producing larger squads after all. The Tervigons are there of course to make more Termagants and support the army with Catalyst (which won't be swapped for Biomancy powers unless other psykers roll nicely and get good options).
You then have a lot of room to work with at multiple point values. Tyranid Primes can make the Carnifexes tougher and bring more combat ability to the army (which can move around due to IC status). A 3rd Dakkafex could also work though these guys aren't exactly cheap. Otherwise running that final Heavy slot with Biovores to flesh out ranged anti-infantry isn't that bad an idea, particularly since they might actually plink a Hull Point off a tank now for the laughs. Running a Hive Tyrant or two instead of the Primes also works - one if on foot with a bodyguard and OA or attempting to fit in two with Wings + double MC Devs for some extra mobility + vector strikes. Very expensive though. Hell, taking another Tervigon (or two) as HQs works well - more support and more little guys to run around and clog up the enemy. All of these options add more T6 wounds to the pile though (Primes through majority toughness ruling) which keeps with what the army wants but as we discussed, isn't really as good as it was in 5th where it still had serious match-up issues. We need to expand beyond this with other options.
Again, filling out the 3rd Elite slot with either Hive Guard for more T6 + anti-tank or Zoanthropes for anti-everything + psychic flexibility is nearly a must, particularly at 2000 points. One would think there are other options available but you really still need the three anti-tank units and with less active psychic defenses, Zoeys can provide that plus some anti-infantry or psychic flexibility in a pinch. The other options not so much.
With Troops you have several options. Another Tervigon + Termagant squad combination works fine, as does giving the original Termagants Devourers for increased ranged anti-infantry. Otherwise Hormagaunts or Genestealers are decent little guy additions who can really benefit from the new Fearless and assault rules though still assaulting into cover sucks. Both have Fleet which is very important for any assaulting unit as you should know but still suffers from NOGRENADES syndrome. Tyranid Warriors are still far too vulnerable to instant death from missiles and the like and since they are competing with other solid Troop choices and aren't pressuring the opponent that much, aren't a great choice here.
Harpies can sit down. I'm not paying that many points for that bad an MC, even if it does fly. Gargoyles and Raveners are still the best choices here. Raveners still suffer from instant death syndrome but with a now 12" move, RCL and Fleet, are faster than before and quite scary to tanks (a reliable 12" move now rather than 6"+Fleet covers the weaknesses of RCL, particularly combined with Fleet) with lots of Rending attacks. Gargolyes are likewise a unit which gains nicely from 6th ed tank rules but are much harder to get cover for and thus can be turned into a red mist pretty quickly if you're not careful.
Conclusion
Tyranids gained quite a bit with 6th but are still lagging behind other armies for the most part. Their main 5th edition basis does transfer over to 6th edition with the core largely remaining the same (Tervigons + Hive Guard) but with a different support structure in place. More utility and bodies rather than a full-out Zilla style list which spawns the little guys. The biggest change here is the T-Fex really becoming lacklustre for the 265 points you pay - it really needs something else now and with tanks being much more vulnerable in combat to MCs, is far less needed.
Again, filling out the 3rd Elite slot with either Hive Guard for more T6 + anti-tank or Zoanthropes for anti-everything + psychic flexibility is nearly a must, particularly at 2000 points. One would think there are other options available but you really still need the three anti-tank units and with less active psychic defenses, Zoeys can provide that plus some anti-infantry or psychic flexibility in a pinch. The other options not so much.
With Troops you have several options. Another Tervigon + Termagant squad combination works fine, as does giving the original Termagants Devourers for increased ranged anti-infantry. Otherwise Hormagaunts or Genestealers are decent little guy additions who can really benefit from the new Fearless and assault rules though still assaulting into cover sucks. Both have Fleet which is very important for any assaulting unit as you should know but still suffers from NOGRENADES syndrome. Tyranid Warriors are still far too vulnerable to instant death from missiles and the like and since they are competing with other solid Troop choices and aren't pressuring the opponent that much, aren't a great choice here.
Harpies can sit down. I'm not paying that many points for that bad an MC, even if it does fly. Gargoyles and Raveners are still the best choices here. Raveners still suffer from instant death syndrome but with a now 12" move, RCL and Fleet, are faster than before and quite scary to tanks (a reliable 12" move now rather than 6"+Fleet covers the weaknesses of RCL, particularly combined with Fleet) with lots of Rending attacks. Gargolyes are likewise a unit which gains nicely from 6th ed tank rules but are much harder to get cover for and thus can be turned into a red mist pretty quickly if you're not careful.
Conclusion
Tyranids gained quite a bit with 6th but are still lagging behind other armies for the most part. Their main 5th edition basis does transfer over to 6th edition with the core largely remaining the same (Tervigons + Hive Guard) but with a different support structure in place. More utility and bodies rather than a full-out Zilla style list which spawns the little guys. The biggest change here is the T-Fex really becoming lacklustre for the 265 points you pay - it really needs something else now and with tanks being much more vulnerable in combat to MCs, is far less needed.