Dunno if anyone has leveled up Teebo's leader skill all the way, but so far, this is what I've got:
Leader: Guerrilla Warfare (affects all Allies)
Level 1 = Allies have a 30% chance to gain Stealth for 1 turn at the beginning of their turns.
Level 2 = +5% Stealth Chance (35% total)
Level 3 = +25% chance to gain 25% Turn Meter at end of turn
Level 4 = +5% Stealth Chance (40% total)
Level 5 = +5% Stealth Chance (45% total, Req. L50)
Definitely going to play around with Teebo a bit more and see if this is viable or not. Fun, anyhow. :)