He works pretty well under Palpatine lead. I use him a bunch in GW. His Offense Down debuff sticks well, which makes Rey a non-issue and is great at cooling off that enemy DPS. Since his TMR on AOE has a 45% proc rate, it usually only hits 1 or 2 enemies and doesn't do much damage, so it seems better to just focus his basic on the key threat.
I don't use him in Arena, he's a little too soft for what you get out of him. If his TMR had a higher proc rate, I might put him in.