Let's review:
Quelling Blow – Deal Physical damage to target enemy and dispel a random positive status effect on them. If an effect is dispelled, Plo Koon gains Defense Up for 3 turns.
R: A joke. Defense up for a tank without taunt makes no sense. The dispel only removes 1 random buff, so, if you hit a tank with taunt and 1+ buffs, there is no guarantee that will remove the taunt (RNG smiles to you). Remove defense bonus and make his dispel remove all buffs and will be great.
Force Judgment – Deal Special damage to all enemies with a 55% chance to inflict Offense Down for 2 Turns.
R: This is the only useful skill.
Take Charge – All allies gain Defense Up for 4 Turns. Clone allies also gain 50% turn meter.
R: Defense up is "ok", but the power of this skill is the TM boost. Clones are most benefited by the leadership of Rex or JKA. Make this TM boost apply to Jedis too and we have a great skill, improving his synergy.
Overwatch – Each ally has a 50% chance to remove Stealth from each enemy at the start of their turn. If they dispel any enemies, they gain Offense Up for 1 Turn.
R: This is the worst leader skill of the game. It is so terrible that I do not even know how to improve it.