Bring the player not the class, to use a WoW phrase. As long as you aren't running all dps, everyone should be able to tackle a boss in a non-infuriating way.
No, the only thing you can do while he's casting is interrupt via a knockback. THEN a short time after one person does a knockback (you only have one per person) another person has to do a knockback and THAT knockback actually works.
Also you will have to kite him over to the walkway beforehand, as he will literally stand in one place even if you're across the fusk!ng room, so if you didn't do that, or have a person with a pull or stagger knockbacks, he is immovable and invulnerable.
Or imagine this monumental concept, you actually line of sight his lightning to get him to move. Stop whining that you brought the wrong composition to do a fight. That is nobody's fault except your own.
I have personally enjoyed the interesting encounters in this game. Please don't dumb them down the way WoW has dumbed down instances. This game has flashpoints with boss encounters you don't normally see outside of operations. Take the mentor encounter in Directive 7. Now people come upon a fight that isn't just omgroflrollover and complain that they can't do it with every single group composition imaginable.