Mace is horribly outdated. He was never all that great, and now he's just old, busted, and additional busted.
Here's an idea I had for how to make him worthwhile again. Changes are in italics.
Deal Physical damage to target enemy. If Mace has Protection, this attack deals 50% more damage and he gains Taunt for 1 turn. If Mace has no Protection, he recovers Health and Protection equal to 50% of the damage dealt
Deal Special damage to target enemy and remove all positive status effects. If any effects are dispelled this way, also inflict Offense Down and Critical Chance Down for 2 turns. This attack deals 40% more damage to Sith.
Jedi allies gain 20% Offense, 10% Critical Chance, 10% Critical Damage, and gain 8% Turn Meter when they score a Critical Hit.
At the start of each of his turns, Mace has a 70% chance to Expose a random enemy for 2 turns. This effect can't be Resisted. In addition, Mace gains 25% Turn Meter whenever he attacks an Exposed enemy. ZETA: Enemies that attack Mace while he has Taunt are Exposed for 2 turns, which can't be resisted.