I'm betting that right now Blizzard is thinking the meta is healthy because no one deck has taken over too much if you zoom out and take a big picture view. But that outlook is misguided because in the lower ranks Quest Mage does great (because it's cheap-ish and easy to pilot) while at the highest ranks Quest Mage is almost a non-issue because it's suppressed by Garrote Rogue and Lifesteal DH. These decks in turn aren't much of an issue at lower ranks because you can basically just hope they misplay in a way that throws the game and that'll probably happen. While I like that there are high skill ceiling decks in the format, for anyone who doesn't want to play combo decks it isn't a satisfactory answer to say "oh, you want to beat Quest Mage? Just git gud with Garrote Rogue." A balance between various OTK archetypes isn't really the type of balance most players are looking for, and it also makes it challenging to counter OTK decks consistently because you never know exactly which combo you're going to be up against.
I don't think the problem is playing cards for zero mana, but that there's so many different decks that play cards for zero mana right now, that a control deck couldn't reasonably run tools to slow or counter all of them, even if those tools were made available in the next expansion.
I say this because, athough I happen to be a combo player myself, I kinda miss playing against control decks. The buffs to Hero Power Mage and Pirate Warrior didn't really do anything to bring control back, and sadly even if we did, I don't know, give Warrior some combo to generate a ton of Armor against Quest Mage and Garrote Rogue, I just imagine Lifesteal DH not caring and doing like 100 damage. Do I have no idea how to fix this meta, other than continuing to hit United in Stormwind with a nerf bat until it isn't even United in Stormwind anymore.