I would like to see him revamped.
This is another example of a thoughtless design. He's a tank with low health, or a support with low potency and limited benefits, or situational leader for a threat that's yet to surface.
What I'd do with him is pump up his health to that of a top tier tank, combine Force Judgment's effect into Quelling Blow, and include Jedi in Take Charge. His area attack could instead have low chances for Stun, Slow, and Turn Meter Reduction in addition to a remove stealth effect. I don't see anything wrong with is leader ability so long as he gets a decent passive ability. I'd give him a passive similar to a taunt in which he defends the damaged party members making him a true Jedi tank. I see it as something like this:
Whenever an ally is damaged Plo Koon has 50% chance to Defend the next time they are attacked. Plo Koon absorbs damage for defended ally.
Add 25% chance to deflect 25% of damage.
Add 25% chance to deflect. Deflect 25% more damage.
Increase Defend chance to 75%.
Plo Koon absorbs 50% of damage and deflects the remainder.
Add 10% chance to reflect half damage back to the attacker.
Deflect all damage.
Add 5% chance to reflect full damage back to the attacker.