Gunzerker has a few issues

I've been trying to play this class lately, but all I'm finding is he's fairly broken. Keep It Piping Hot is supposed to increase his gun damage while his action skill cools down. It doesn't work at all, the icon won't even pop up. No Kill Like Overkill increases your damage for a limited time based on the excess damage you delt to an enemy you killed, but will not work with shotguns, rockets and some assault rifles.

And the biggest issue, if you're partial to making things explode you probably like Torgue weapons. If you gunzerk with a Torgue weapon in your left hand it copies the damage stat of your right hand weapon. So based on what you equip you could turn your 1200x17 shotgun into a measly 800x17 if you rock an smg, or 40,000x17 if you swap to a rocket launcher. This only applies to Torgue weapons in the left hand, meaning the down and right d-pad slots.