I run Teebo in Arena a LOT and I can say without question that his Scramble Tactics with Omega do not function properly at all. They really never have and it had nothing to do with his leader ability. I use Chirpa as lead and I can't tell you how many times I activate stealth and it only lasts 1 turn.
My opinion is that a turn gets triggered when Teebo gets called as an assist. So when Chirpa uses Tribal Unity (which calls all Ewoks) and when Phasma procs (when used as lead), this gets counted as a turn with Teebo. So many times I initiate stealth and he comes out and i have a 4 turn cooldown.
I'm at the point that when I initiate stealth, I'm not even expecting it for first turn!