1. Someone can be good enough with a champion for it to be ban worthy without it being "OP". People toss the word "OP" around like it's going out of style.
2. Your analysis of bans and picks in SR tournaments is not adequate, at all.
a. Almost all the bans in the recent regionals and world championships are targeted bans. Even if a champion is banned by several teams (Orianna), it's because each of the top teams had someone specializing in this champion - this is similar to how Kassadin is OP, but if your team has people specializing in Kassadin and the opponent doesn't, you might not ban him (ok, unrealistic ), but the point is likely every team has a very capable Kassadin player.
This is often a strategic decision, just like every pro team should have an Orianna player, even if she's not really OP, just so if they're first pick they do not really have to "waste" a ban on her.
b. Seeing the same champions picked and banned is mis-leading to the state of the game, because of the nature of the tournament. Sivir was picked/banned (banned, actually) in 100% of the games CLG.NA played in. Eve was more or less banned or picked in every game M5 played in.
Had CLG.NA made it through the rounds, you'd have seen more Sivir picks/bans, and less of other champions.
You see a lot of specific champion picks, because they're the champions played by the teams that played more games. I'd also be careful about assigning a causative linkage here.
2. Zileas addressed the number of bans issue recently. Bans are always something they want to be careful with, because you do want to see people playing their best champions. Anivia isn't OP on SR, most people would agree. It's Froggen that often makes her that good. This goes along with what happened in the championships, nearly no champion enjoyed a perma-ban due to being too strong, but just due to the team they played against.
Jayce was too strong, yes. Ezreal however wasn't really banned because whoever could picked him, and the other team thought it was ok.
3. I think the point about diversity is more or less flat out wrong. There are always "the best" champions. Let's say we can all decide who are the best 10 champions. So we ban these 10 champions. And these 10 champions are banned 100% of the games, it wouldn't take long before we realize who the next 10 champions are.
We aren't increasing diversity, we're just moving the goal-posts.
4. That's where it all combines. Whoever said "10 bans allow 1-2 counter bans" made me head-desk. That means 8 bans are a band-aid. This needs fixing. And if unfixed, as per point #3, the issue isn't really solved, or even hidden, we just meet the champs who are OP in the new meta (because removing 10 champions basically creates a new meta). All the bans should go to the realm of counter-bans. I guess we can live with 1-2 "must-bans", in any game mode due to the nature of balancing, and especially on Dominion with the special constraints.
I personally talked to Halfey about it before. I believe adding more bans is easy. People are now using it as justification "it works in DD, so it must be right." And 6 bans work on euw, so it must be right too... and I bet if some people had 20 bans, they'd say it works and thus is the way to go. We're looking at how things could/should be. I don't buy that DD needs 10 bans. The more bans you add, the more bans you could add, the more bans some people would ask for.
There'd always be a champion you're frustrated playing against, but in the end what matters is the champions that really break the game, rather than are merely frustrating to play against.
Adding bans is easy, and doesn't really seem to add much to me. You guys say you need all those bans to have some counter bans in addition to the must bans. I feel most of the bans can already be expended on counter-bans. "OP" is a call that is in someone's head, and in part just removes the onus from oneself to deal with the champion.
When I play with Jax, I feel very powerful. I've never been intimidated or annoyed when playing against an enemy Jax, even when I play other bruisers.