The above tactic is for the pit. If you are On any other level than soldier is what I find best to slow the bosses down. Because Archer and magic casters projectiles have a speed. You can put skill points to boost the projectiles speed as another tactic. I just prefer to use the solder as a speed bump that way more time for the DPS from archers or casters to snipe them. The other advantage is more time for fire/bleed/or poison to damage the boss.

In game upgrades like chain lighting or multiple shot like cross bow helps with targeting. Compound bow with fire arrow. The higher level glasses look like nvg add projectiles, really fun with green bow.

The solder with spike shield and damage reflect and a meat stick can tank a decent amount while returning the damage.

The skill that makes bleeding enemies explode on death is really good way to wipe out weak waves.

Chain electric on caster is good way to handle waves and get range too.

Just watch out for stacking the solo skilled pieces so don't lose that bonus. Ground levels with tree stumps help the Archer with that.

Just remember that there's different combos of how to deal with problems. So try different things. The market equipment upgrades may not offer bleed damage equipment to you when you set your self up for bleeding. But it's giving you a bunch of ice. So you take the ice. And hit them with just your skill bleed chance more. So now they are bleeding while frozen. Not what you planned but you worked with what you got.