I use steam controller - so for me any gamepad support should be okay. Maybe just allow to makeevery action with single key

Not at the moment and I hadn't tried to play it with gamepad yet.

Okay, maybe It isn't problem with a keys - character can stuck with moving diagonal, and pressing down won't return him to moving only left - he will keep moving down left

Yup. I had a break from the game, but now I have it almost everytime, while few weeks ago I never had this problem. It looks like not every keyup even is being registered. Or maybe server doesn't get command?

Also, maybe increase hp of grunt? Now properly done combo (whirlewind + alt attack) means at least 2hp damage, which to often means kill, specially when connected with fast attacks. Maybe help somehow with standing up?

Maybe instead nerfing Berserker buff grunt? I would slower a bit Berserker attacks and git grunt way of interrupting zerk special attack - maybe by grunt special attack? IMO there is nothing bad with requiring a bit more experience with playing one class over another.