In a nutshell, his basic debuffs enemies, his special buffs allies and calls them to assist. He also passively buffs allies every time they use a special. When he calls an assist, all other characters with his Translation buff attack too.
Both his buff (Translation) and debuff (Confuse) stack up to 3 times. Each stack gives additional bonuses / detrimental effects. The first stack of Confuse prevents buffs, which is great to keep tanks from taunting. For example, if you're facing DR you want to confuse Malak and Sith Trooper so you can go after BSF and HK.
His buff / assist call goes on whoever doesn't already have it or has the least stacks of it. E.g., if Padme and GK already have Translation because they've used a special, while JKA and Ahsoka don't have it, you want to put it on JKA to trigger a mass assist. (Ahsoka assists anyway when 3PO uses a special).