You have no right to cancer other decks if you play Midrange Shaman, even brutal turn 4 win face aggro pirate. And yes, until Renolock/Goon Paladin and Dragon Priest become meta (if), it should be still easy to win with it.
Nonono) "Cancer" is a deck which goes which strictly goes to face no matter what, like pirates or say aggro hunter at the times of HS beta) Midrange shaman is a deck where you have to think. Time to time :D
It's a bit less autopilot than other people think. From a deckbuilding perspective it's pretty cut and dry, but the gameplay aspects in the mirror are actually skillful at times, overloading a lot on one specific turn so that you have more full mana usage two turns later. At least Mid Sham makes trades, like Zoolock. WoToG-Aggro Shaman, Face Warrior, and Face Hunter are definitely degenerate though.