I think there's a number that adds up your MMR values across the board (with different factions). Was referring to that one, so two default values, I think. 50% WR or so. None of the decks I run are meta (movement/Aglais shenanigans as SC, Artis+berserk/bloodthirst stuff as SK, Harmony Master Mirror when i feel like going full retard), and it's still 50% in pro, so go figure.
And has the correct tools to shut it down in the first place. As an NG player you automatically assume fuckloads of control, which just isn't (and shouldn't be!) true for many decks.
Cahir doesn't come alone. It comes with Ffion and Letho, and shutting THAT down requires a dedicated control or movement deck. Best case scenario is that you have a purify and then two instances of movement/locks, which is awfully specific. Either that or three very hard removals. And just one instance of Cahir is enough to negate EVERY boost you receive. And considering you may also have to deal with Damien or Skellen later...
That's not to say it's impossible. Triple duel can handle it all just fine, sure. Until it gets nerfed, which is long overdue. The rest of the decks that aren't made of 99 nukes? Not really.
Also there's way more boosts in the meta than you claim. Symbiosis, Firesworn, Passiflora, anything SC...heck, the only situations where Cahir fails to find value are memes like Blue Stripes and broken-ass SK Warriors.
I'd say "in-game polls for eligible accounts", but this kind of chaotic democracy often leads to stupid consequences. Still, it makes more sense than making game unfun for most everyone sans tryhards. Besides, bad cards don't get bad rep for nothing. If something in the game forces you to stick a very specific counter in your deck or makes a whole class of playstyles non-viable, this something begs for (at least an indirect) nerf. By this criterion, the Ball and Cahir are among the worst cards in the game, only kept in check by dominance of SK warriors in meta, but meta could change any patch...