Baron Fight on Deviantart

I've seen more jungle Ashe than jungle Yasuo. His kit is more suited to gliding across minions and wrecking laners than ganking. I mean, he needs to use a spell three times to use his sole point of CC. At least Master Yi can press R, dash out, and immediately slaughter people.

But in this case, I would hazard a guess that the Teemo really is the jungler. There's no off meta AD bruiser/assassin to use in place of a Marksman for bot lane so it kind of pigeonholes Ashe into that position.

The alternative would be ADC Yasuo and Support Ashe with Jungle Leona. I've seen ADC Yasuo's rekt face, and I've seen a Jungle Leona work out (our team really underestimated her and let her get a couple of free kills to their ADC). I have seen a Support Ashe before and it did do well ... but Jungle, Mid, and Top lost lane entirely or fed a few kills to their opponents so we lost overall that game.