Some tips that are not mentioned in this guide:
All bosses: You can reset them to lower their BP, do it always to make things easier.
3 Boss: A berserk alone can solo them, so its a good idea for a P-dps to switch into him in case things go wrong. Throw a blade acrobat or a fencer in the middle for insta BP.
Lucchese: Instead of bringing more than 1 healer, just dodge the tiny circle when he has < 40% HP. This circle not only stuns you, but takes -15% hp per second and sometimes you can't even reach the purple fire in time.
Cerberus: Tank blessing is completely optional. If all the party stays in the border of the green circle, Cerberus will stay in his spawn without moving. Also, not sure about this but I think this boss has very high phys resist.
Asmodeus: Try to overcap dark and lighting resist since he lowers a lot. Equip the lvl 55 necklace that removes debuff so you can remove his bomb and his -30 resist debuffs quickly. Bring a yellow human class or any class with pushing skill to push the boss to the door, makes things much easier, and allows P-Dps to survive him.