Psychic defence; is it really necessary? Yes and no (don’t you love me?). When available easily and with minimal cost such as Space Marine Librarians/Rune Priests or Farseers with Runes of Warding, it’s almost a case of why on earth not? Other armies like Imperial Guard, Witch Hunters and Daemon Hunters have the option to do so but generally don’t and IG and WH still produce effective competitive lists. And some armies just get it for ‘free’ such as Tyranids; the lucky gribblies. Others however, have no choice. Dark Eldar, Tau, Chaos, Orks, Necrons and Daemons of Chaos are starved for anti-psyker abilities (though there are some counters, there is no stringent 4+ stops psy power, etc.). However, some of these armies are still quite capable on the battlefield and importantly one of them is brand new. What’s this mean?
Ignoring fluff and all of that crap, GW has decided to bring psychic powers back into the mainstream of 40k. Even before 5th edition got underway Orks, Chaos and Daemons of Chaos all had some hefty psychic powers related to their codex releases in comparison to what they had before. As 5th edition army books got released, it was ever apparent GW wanted psychic powers to play a role in today’s game and it seemed like a sure thing each new army would not only have access to decent psykers but decent psyker defences. DE shoved that theory out the window with no real access to either. Which brings us to the original question, is psychic defence necessary?
Psychic defence is obviously a good thing to have as it gives you a 40-50% chance of stopping some very impressive offensive and defensive abilities of the opponent. However, it is not a requirement of competitive lists as exemplified by IG, Tau, Dark Eldar and Witchunters even though both IG and Witchunters have access to psychic defence (the others have no choice). What this indicates is psychic defence is not a necessity, even when available and obviously depends on the list and army. Looking at the new Marine books all of their psyker defences come on a cheap HQ with excellent utility in being very defensive (tempest, shield, storm caller, null zone, etc.) and having some excellent offensive powers, too (avenger, lightning, blood lance, sword, etc.). Compared to the psychic defences accessible in other armies these units don’t just bring psychic defence they are a good unit in their own right.
This then comes across as psychic defence simply being a bonus for Marine (and Eldar/Tyranid) lists. The units with psychic defences are very useful in their own right but the lists would manage fine without them; rather than relying on psychic defences to defend against offensive psychic powers, there are actual tactics you can use against them. Consider competing against a BA Jumper list with a Libby and Blood Lance. Even if you have psychic defence, castling up and clumping all your tanks together is a bad idea. If that defence fails the Libby could hit more than 5 tanks with a single shot. Against Lash most people simply mech up and demand the sub-par Chaos anti-tank try and break open lots of cheap transports. Etc. There are obvious exceptions which you cannot defend against such as combat powers (i.e. warptime, sanguine sword, etc.) and you can’t really stop defensive powers (i.e. Null Zone, Shield/Storm Caller, etc.) but that’s part of 40k balance.
In the end, psychic defences are basically a bonus to an already good unit and lists are quite capable of being competitive and balanced without them. In army books which have access to good psychic defences such as Marines and Eldar, when not taking the psychic defence unit the opportunity cost of losing that must be weighed but it isn’t a clear cut “you must have psychic defence.” It’s a nice security blanket to have and can disrupt your opponent’s plans but by no means is it necessary.
