It can definitely be used to pull off some insane damage really quickly if used on the right card. That said, you have to consider the conditions necessary to make it overwhelmingly strong.
- As you pointed out, it needs to be used on a high cost monster for truly overwhelming damage to be done.
-That monster has to be able to attack right away or you make it a clear target for any removal/control cards your opponent has handy.
- You need to have the health to deal with attacking any taunts on the board.
In order to bypass these conditions you probably need to already have pretty decent board control. In this case the windfury is probably just hastening the inevitable.
You also have to consider that it's quite likely that the shaman will have had need of windfury's effects earlier in the game and may have used it up on a weaker card that likely didn't last very long.
Compared with a lot of things other classes can do with a single card, windfury is pretty easy to deal with.
My first deck i had both windfurys in it, wasnt much help as i would always seem to draw them easrly and theyd be taking up valuable hand space. So then i went down to 1 in my deck. Was a little better and more helpful. Then i took them both out and just kept in my 2 minions that can give windfury and ive won sooooo many more games.
In short windfury is very situation based and is more often then not a detrement as it takes up deck and hand space, however in those perfect situations i can be very devistating but most class's have cards that are extremely devistating in certain situations. That and weighed against having 2 minions in your deck who can give it to another minion and you get a bonus 3/3 minion on the field it flails in comparison.
I have a deck right now that uses Windfury, Minions with Windfury, Minions that buff other minions with Windfury, and buffs(that help Windfury).
Plus buffs upon buffs(Bloodlust, Flametongue Totem, and battlecry's).
But...I wouldnt call it op by any means, just need the right synergy with it that makes it look op. =)
Threats of violence. We take these seriously and will alert the proper authorities.
Posts containing personal information about other players. This includes physical addresses, e-mail addresses, phone numbers, and inappropriate photos and/or videos.
Harassing or discriminatory language. This will not be tolerated.