From what I fought and won, it's not necessary to form a team with skill like that. But it will make your life easier, if not highly recommended. It just like those unique mission that asked you to form specific themed team to tackle the stage yet you can simply power blitz them if you're strong enough. I simply use counter and nuke team to blitz through with the rest 2 as sweeper.

So after trying the broken boss couple of time (and failed as I can't beat its third form) It's really is broken boss that tailor to whale. It got some of the most broken skill ever.
The boss got no weakness, so no weakness damage boost here.
1st form is easiest yet still hard, got 20% atk buff and 10% accuracy buff. It got quite low hp however.
2nd form is harder now, got 30% atk and 10% accuracy buff. Average hp and average def.
3rd (and supposed to be last) form is broken. It got 30% atk and 10% accuracy buff... and will stack its atk by 10% each turn passed, which carry on to other team fight.
All form hit 4 targets, and hit hard. So provocation won't help you much here as well. I still don't know what team is the best against this battle. It would be good as permanent challenge, but as limited time event... not so much.