I think maul is completely fine as he is. His kit is amazing from the aoe daze to the 100%tm gain with his basic on a killing blow. His awesome unique including his zeta leader, puts him at my favorite character right now.
Now I do think something needs to chant with savage. I think savage should get a zeta that's puts this duo into the meta.
This zeta will go onto savage unique.
Whenever maul(or sith) is hit(or crit); savage taunts for 2 turns and gains crit immunity.
Now if you don't want that I suggest give them a small synergy.
If maul is present: gain speed up and offense up for 2 turns, on evade or crit on maul/savage.
If savage is preset: gain 20% extra tm and get offense up for 2 turns on evade.