ARURF [Master Yi vs Sona]

So, why is it Sona is permabanned on ARURF, but Master Yi isn't? It was to my understanding that Sona was permabanned due to the inability to fight her/kill her 1v1, due to how her kit works. That, or her heals were just too effective/annoying for the game mode. This is completely understandable.

HOWEVER, Yi can fight an ENTIRE TEAM by himself, once he gets 2 items. [ ]

So, I'm curious, why is he not permabanned like Sona, if he is worse than her?

'Oh, but you can at least fight/kill Master Yi, early. It's ARURF, so it shouldn't be that hard.'

Yeah, except we're forgetting that it's ARURF and that the gamemode involves so much chaos that either your team doesn't wanna end due to trying to hunt for kills OR the team's champion comps are (on a VERY VERY rare occasion) balanced enough that the game doesn't end fast enough OR you get unlucky and have not a single bit of hard/targeted CC to hold him down long enough to kill him. Let's not even get into the fact that he can practically stay in lane for however long he chooses thanks to the heal on his W.

Seriously, what gives?