Even when you compare WTF's cards to decks like $tax, Slaver, 4cc, etc., WTF comes up really short in power level. Even the creatures themselves aren't very intimidating compared to 7/10's, 11/11's, smiling 1/2's, and little green monsters that have a habit of getting bigger. This deck doesn't do anything particularly broken and really only has four hard counters with out Voidmage. Isn't Spiketail and Daze easy to play around in a format with Moxen, Lotus, Workshops, etc? Even with Null Rod in play, isn't it easy to play around?
Instead, why isn't there a deck like CounterSliver that has the same basic premise, yet with obviously better creatures?
First of all, the deck wins most games via tempo. It's hard to explain just how good it can be; like fish, you really have to play it to understand how it all comes together.
Countersliver has really bad creatures, actually, and no good draw engine, since you can't play curiosity. All the slivers can do is attack--that's not true at all with this deck, which is why this creature base is so ridiculously amazing. Plus, Crystalline Sliver is white (ugh), and you have no good 1-mana or 3-mana slivers. Finally, slivers are only worth playing if you have out at least two, and you need 3 to make them good. That's serious over-extension; you'll just lose to balance/deed/etc.