This a a very basic guide to the bosses.
Surgeon
So for this guy, take two guns and one shield. The shield MUST have the “Blacksmith’s Grace” skill.
The strategy is: have the guns kill the minions, have the shield “entertain” the boss. Keep the guns on the edges of the room, since sometimes a minion spawns right there and is an easy kill.
When you start out, kill the two minions closest to you, or at least one of them.
Once the fight is underway, use the shield to pull the boss back towards where you started, and have the guns slowly move to flank/backstab him.
If you use Blacksmith’s Grace on the shield, you can survive through basically all of the bosses attacks.
The Shadowround skill on the guns is nice but not mandatory. If you bring it, make sure you use it on both, use it first, then fire. You firing will make the other shadow shot skill proc, then your shadow shot will proc off that. Basically you’ll attack 3 times in 1 turn for each action you take.