I miss Raum on the list. The guy is unkillable if the team has no CC to stop him. Most annoying tank by far. A Torv can be killed or countered by wrecker. But Raum can only be countered in the picking phase. That might not be a big problem for high skill matches with actual counter picking but for those 99% without it's shit.
I also miss Io, our beloved 2in1 healer-tank hybrid. Judged by her winrates at Platin/Diamond she is still OP. Did they even implement the cauterize-Luna thing?
I don't think the listed 4 flanks are OP. I also heard complains about Koga or Buck. A good flank is annoying. Vivian is maybe. A 4K HP pool with scape goat V is unique for a damage champ.
I don't agree with the easy to play but can do a lot idea. Since teams are mixed putting silver and Master ranks together an OP Evie can ruin the fun as easy as an OP Vivian.