Earthquake is 2 cards advantage and this is 6. Earthquake costs 3|2, this costs 8|6. This card is roughly 3 times the cost of earthquake for roughly 3 times the card advantage. Cards do not scale evenly with cost though as bigger creatures and effects are simply more efficient in the long term. This, however, is counterbalanced by the fact that your opponent is normally rewarded for playing as many of their cards as possible. In the case of Earthquake, this means they are constantly trying to maximize your potential advantage, whereas in Wind Sweep's case they're aiming to minimize it just through normal play.
TL;DR - Wind Sweep is a little bit OP under perfect conditions but will quickly become UP as the game progresses and is next to useless in multiples. It is fair, probably on the weak side, and could likely benefit from a single quanta cost reduction but, due to its potential annoyance factor, might be better off staying as is.
