Going through the forums it seems this opinion is not uncommon, but I don’t think I’ve seen why it’s confused and roleless ,so I guess I’ll try to explain it here.
Brain Burst just… sucks, on higher difficulties, namely 4 and 5, you really can’t kill priority targets reliably. I thought it might change once I hit level 25 and unlocked 6 Warp Charge stacks but no, even with 6 you can’t BB dogs or Ragers in one go. It get’s even more frustrating when your Veteran does everything you can do, better than you by a mile, with their only limitation being ammunition that they constantly generate for doing said job. No clunky charge time, no slug move speed, no venting to not die, just point shoot and kill. I guess Ogryns are an exception but the Boltgun and Plasma gun exist. Not to mention Veterans active ability is way WAY better than Psykers, why is Psykers like a quarter of unchained’s active. It’s awful and I almost only ever use it to save myself from accidentally exploding. Staves are good I guess, they kill hordes and thats enough to be good but it doesn’t really solve Psykers problem of not having any real role in the team.
Oh and don’t even get me started on their penances, Blow yourself up and kill three elites… great. Basically solo a boss, the change to 90% makes no difference considering I basically did solo a boss with BB and still didn’t get it.