yasuo's ulti
i was in an one for all game as
vs 
and appearnly he ulti counts as a "teleport" rather than a "dash" even though you can clearly see his model dash toward to your champ when he uses it.
now in the VAST majority of the cases in the game chaning it to a dash will have no effect.
i am not sure if he can cast it while rooted but imo he shouldn't be able to.
so only ground effect skills or insanely lucky aoes could hit him mid flight.
but it would aoffer some interesting and rare counterplay. as well as giving him at least once decently hard-counter in
. (who btw i dont play)