Yi should be nerfed in ARAM
I've played quite a few ARAM matches, and there is no champion I've seen who can unbalance a match quite as quickly and brainlessly as Master Yi. With the limited space of the bridge, dodging skillshots is more difficult, which gives certain champs an advantage (Lux, Twisted Fate and Miss Fortune, for example), and the availability of walls helps Poppy and Vayne. Master Yi, on the other hand, has an overwhelming advantage in the limited space; once he ults, it is not his problem to deal with you, it is your problem to deal with him.
There are probably a dozen different ways to nerf him in ARAM specifically (there are ARAM-specific items, after all), and Riot needs to implement one.