I think an interesting mechanic would be to implement a sort of "Perils of the Warp" where if a librarian/sorcerer is going absolutely ham with his abilities a bar is filled up. Depending on what they're using and what equipment they have will determine whether they suffer a Perils of the Warp gruesome death if that bar is maxed out. Or the bar itself could just be a representation of a percentage chance for that Perils of the Warp to occur.

^ Perils of the warp make for a good risk vs reward

Make a failure modifier for pskyer abilities, all of which are charged up and fired. The farther you power it up the higher % chance you have at suffering a catastrophic failure. It will also keep ability clutter down as well since instead of having multiple abilities with their own risk you can have one or two with power variations that lead to increased risk for power.

Bout Perils of warp, maybe just not blow themselves up, but also people around? Librarians being a heroic unit, the skill to play one right and not only exploding 24/7 should already be present.

stone tablet?
okay, I think you just one-upped everyone who was religiously following this game.

You better hope there is a cult of Tzeentch or someone is going to get their head popped all the way from my living room...

Eldar psykers are a must have! I wonder how they will balance all the races and classes.

More indirect means of attack are needed. Spells that cause disorientation,reversed compasses and maps, giving false orders, listening to enemy comms, fucking with player's controls things like that.

With Perils of the Warp you could have some fun with it. Rather than just taking damage have a range of potential drawback. Suddenly the pskyer is a Warp Rift with NPC Daemons pouring through...

Though given the PVP aspect a random chance for 'x' to happen may not be the best. Would be cool to see the in direct side effects of psychic powers rendered in game, unnatural frost around the psyker, the walls start bleeding, shadows lengthen or contort.

I was kind of hoping psykers could counter another by challenging another psyker to a mind duel, to which the screen goes black and opens a pong game between the two players as they engage in a battle of the minds.

WEIRDBOYZ IZ MAGIC THEY IZ. WAAAAGH!!!!