There were times in the past when Control Shaman wa a viable deck, but it’s safe to say that we haven’t seen one in a long while. Even though Shaman’s Classic tool kit has some solid Control tools, it always lacked two things – big AoEs and a win condition.
Rise of Shadows has pushed Shaman cards to the limit. Nearly every single card from the set is very good (which doesn’t happen often), which is the reason why Control Shaman might finally exist. Between a big AoE (Hagatha's Scheme – sadly it’s not very consistent, but it works okay), life gain (Witch's Brew) and solid minions (Swampqueen Hagatha, Walking Fountain), Control Shaman finally has what it takes to be viable. While the deck is still not perfect (e.g. it has to resort to playing some Overload synergies to fill the early/mid game curve), it works much better than it did over the last few expansions.