Wow you guys really think Yi is bad? I main Master Yi and when I play dominion I win 9 times out of ten and I often get first place on at least my team. Yi in my opinion is a very strong champ at dominion because he does lots of damage as well as he has a lot of mobility. Most Yi players though do not know how to build him right. I start out with Zerkers and a Vamp Scepter and rush a sanguine blade, because it gives insane damage and life steal and allows me to snowball, from there I get Phantom dancer then IE, then Ionic spark, also i think the summoner spells they pick are very important, I use cleanse and ghost for yi because cleanse allows me to break free of all that pesky CC
tl;dr Master Yi is very viable, you just have to play him right. If you get stuck with one tell him to rush a sanguine blade itll do wonders.