best team formation: have Veradux and Amber Equip amber with Paladin's full outfit (including weapon) you recive his full outfit by killing Paladin a number of times, if you do this she will sometimes do 2000+ damage.
keep Veradux the same outfit except change his weapon to a more powerful one.
i completed it fully (killing all four major bosses) 2 times. assassin is best class
hints for major bosses:
Ignition: just keep attacking him, if fate occures either use subversion on person with it on.
Omen: when he does Dark Omen use break on him, it does major damage and he cant attack you or your team mates.
person with 1 million health: once he is below 990,000 he will heal himself for 2000000 health just before he heals use Subversion on him to kill him.
Sinjid's Shadow: at start disrupt him so he cant one hit kill you. then if he ever reaches 100 focus do disruption again, if you dont have it either break or shatter bolt him. when he hasnt got 100 focus keep on attacking him.