Card that costs 10 freaking mana wins games. News at 11.
Other 10 cost, game-winning cards can be played around. Deathwing? Save a taunt or hard removal.
Varian? Save a board clear.
Y'shaarj - Removal.
C'thun? Keep your life total up, keep a board presence and save hard removal, or steal it with Syl.
N'zoth? Board clear, or play Doomsayer and kill their syl to give it to them, or be so ahead that bringing up a bunch of minions doesn't actually do anything (just beat an Nzoth Rogue who summoned 6 minions and then died to Gorehowl + Bash).
How do play around Yogg? It generally clears the board, gives your opponent card advantage, is a Mysterious Challenger, deals a bunch of damage to your face if the minions are cleared early, and if that's not enough, it frequently summons a bunch of minions for your opponent. Nothing better than your opponent going from no board to Ball of Spiders, Kara Khazam, Force of Nature, or Call of the Wild, going from no cards to a full hand of cards that they don't even run in their deck, going from a losing position to a dominating one.
Yogg-Soron is a minion that is only played from behind and only done so because it has a strong chance to just instantly win you the game, making every turn leading up that one pointless.
What other 10 mana card is played from behind to salvage an unwinnable game? Uh, Deathwing. Except Deathwing has a huge downside, which Yogg rarely does. Sure, once it a while Yogg will discard your hand for you, but who cares if you lose a game you were already losing?
10 mana cards should be strong, but not this strong. There needs to be counterplay.
The only counterplay to Yogg is hope you can kill them before they draw it. So, what's the point in playing slow decks? You guys say you don't want to face Shaman and Hunter and Dragon Warrior but what other choice is there in a metagame where Yogg exists? What's the point in playing Control when long games are decided by a bunch of coin flips?