Slivers are fine. I mean an actual sliver tribal deck. It's fine. Yes, it can quickly get out of hand, but building up a big board state and winning with combat damage is the most fair way to win the game.
I played when Slivers were first introduced. I played when one-sided Slivers came out. I've played against Sliver tribal decks. They're fine. Heck, I even like them. I'd make a Slivers deck except I think they're weak in a Singleton format and I don't wanna play a five-color deck.
Eldrazi, on the other hand, can go straight to Hell.