I don't think Yi is that bad on Dominion when played smartly. I love running Cleanse/Exhaust Yi and I've had a good amount of success with it, once he gets a major item or two he can really dominate.
At the same time though, he does have his weaknesses. CC chaining on him is an absolute nightmare to deal with, but in the skirmished based environment Yi can thrive if you have some good team players to back you up.
At ~1950 elo I've done fairly well with him. Then again, I'm much more of a Riven player when it comes to mah melee deeps.