This goes hand in hand with the review we've been writing for Necrons (and every other one we've done) but I thought I'd give it a dedicated post since it seems to be a recurring issue for some. Every army out there is more than just a bunch of parts put together. It's more than just units A through Z chucked together to ensure there is enough anti-tank, anti-infantry, ability to hold objectives, deal with deathstars, etc. These concepts are indeed important and knowing you can kill X Rhinos or X Marines over a game with your army is important. Too low and you're going to need to rely on ways outside of actually killing your opponent to win. This certainly is possible though leaves one of the most direct routes of impacting your opponent's gameplan, namely killing them. Digressing...
Taking out a single unit can affect how the whole army works in ways which might not show up on paper. The most obvious scenario here is taking out a unit which buffs lots of other units. We often call these utility units such as Librarians or Hive Tyrants and whilst they might have their own direct affect upon the game (Tyrants are beasties in close combat) removing them takes away more than just their direct application. Without a Librarian you have no psychic defenses for example nor any of the excellent psychic powers they bring to the table. This is less obvious for some units however and is often part and parcel of the rules. Taking out all of your Troops bar two small Scout squads may improve your math numbers drastically but within the paradigm of 5th edition you're going to be screwed when trying to hold objectives at the end of the game.
This is a phenomena generally seen outside of Marine armies and something armies like Necrons & Tyranids embody quite a bit. Individually their units are good and work best when working together as a cohesive force. The problem here for some armies (Tyranids) is this makes the army quite easy to take apart. This same issue can be seen when too many points are sunk into 'combinations' which generate more than what the paper suggests they would. Having stuff beyond the numbers is great but you still need to be able to deal direct damage to your opponent more often than not.
Furthermore, just because you have a nice combination or there is a bunch of stuff working behind the scenes to make your army better on the table-top, doesn't make the army good. If you need unit A to provide something for unit B which does something for unit C, etc., well as above your opponent is going to be able to disrupt your army pretty easily. Now if units A, B and C all did something for each other whilst also being good at other roles, losing one unit isn't going to make the rest just plain ineffective. This is where a balancing act comes in whilst list building.
So what's this all trying to say? Two things really. Firstly, an army is more than what it appears on paper. This isn't to say any and every unit can be used to make an uber list - there are restrictions and going for too many combinations or simply not having the direct firepower is going to equate to an army which doesn't have the tools for the job. Secondly, reviews are never, ever going to look at every single combination - there's just too many and we might not have thought of or experienced them all. This doesn't make the review invalid - the review is giving you the information about the unit and telling you why it's good/bad, what it's good/bad at doing and how it does it. You should be able to extrapolate this with other unit reviews to make the whole concept of an army list.
