The Psyker Surge Staff feels lackluster as it tries to fill to many roles at once, it never kills more than 3 to 4 dregs in a horde per cast and the stun doesn’t last long enough to be useful for holding down a special, the single target damage also is lacking when you have the head crush for that.
I think the Surge Staff should go all in on one this like a high damage multi-pierce horizontal lightning bolt that would make it deadly at the start of a horde when they are more lined up or a super wide long stunning “surge” that makes it great for halting a horde for but a moment to catch your breath or give time to pick up an ally
I doubt these ideas will ever even be considered but i think the surge staff needs something to make it more unique as it already has the cool factor with the lightning but it feels like the effect doesn’t live up to the idea you have before using it