When using one of the psykers staffs, the one that works very similar to the conflagration staff in vermintide; I seem to be exploding when I dont want to. And its not a skill issue. When using the force staff to charge up the explosion ground attack if you then hold r to quell and release the right mouse button the staff still charges up. This has caused me to explode like 5 times because I release the keys in the wrong order.
Quelling should always override whatever the psyker is doing, whether its in the middle of an attack or whatever.