First Impressions

After playing a few games on ladder:

• The concept does work: windfury on turn 5 doesn't happen often, but on turn 6/7 is not unusual. Decks that don't interact with your board much are easy prey.
• The deck doesn't have much headroom to recover from disruptions. In particular Shaman is a problem, with AoE and a strong counter-push.
• The weakest card in the list is probably Loan Shark: the coins rarely made a difference.
• I'm wondering whether Lorekeeper Polkelt might be better than Taelan Fordring, since the effect goes off immediately and is guaranteed to go off: Shaman and Mage run transformations while Priest runs or discovers silence.
• Battleground Battlemaster feels strong. Even when it's not lethal immediately, as a 5/5 it often just sticks around.

Game Plan

The key card in this deck is Battleground Battlemaster, which gives adjacent minions windfury. To make sure we have minions on the board that can attack, we use stealth. There are also buffs from Ashtongue Slayer and Abusive Sergeant, repeatable with Shadowstep, to increase the damage burst.

We should be able to get at least 12 and hopefully 20 damage or more from the windfury turn; the rest will have to come from chit damage. With stealth minions and Counterfeit Blade it shouldn't be too hard to get some extra damage in during the early turns. Don't trade unless you have to.

Which turn should be the windfury turn depends on which minions you manage to stick, how much face damage you got in before that and which buffs you have in hand. I'm thinking that turns 5/6/7 are the most likely candidates. While you don't need to win on the windfury turn, you're likely not getting much damage pushed after it, so don't commit too early.

The extra coins from Loan Shark are intended to pay for additional buffs on a windfury turn. Since this is not a combo deck, it's not a hard requirement to save them, but don't spend them early unless you get a lot in return.

Doing two windfury turns can be an option if you happen to draw both copies of Battleground Battlemaster, but the deck doesn't have enough card draw to force this in every game.

There will be a delicate balance between using minions and buffs early for chit damage versus saving them for a windfury turn: every extra attack counts twice with windfury, but you only have a limited amount of mana and postponing the windfury turn gives the opponent more time to find counters or threaten your life total.

Since Taelan Fordring will be in a lot of opposing decks as well, it can be worth saving Backstab or a dagger charge to pop the shield. Then use SI:7 Extortion or the immunity buff from Ashtongue Slayer to remove the body.

Mulligan

Look for a curve:

• Spymistress or Worgen Infiltrator on turn 1
• SI:7 Skulker or Sneaky Delinquent on turn 2
• Loan Shark or Greyheart Sage on turn 3.

If you're on the coin, you could consider going for playing two smaller minions on turn 3 instead, for a more aggressive push.

While there are enough opportunities to draw Battleground Battlemaster (two copies + Taelan Fordring), the card is so key to the deck that I think it's still a keep. It might depend on the matchup though. In any case, you shouldn't have to hard-mulligan for it.

Replacements

Infiltrator Lilian could be replaced by a second Burrowing Scorpid.

Counterfeit Blade is there mostly as face damage: the deathrattle copy is a bonus if it happens to align with cards you played anyway. Nitroboost Poison could be a replacement. Another option would be Cold Blood. If you find you're short only a little damage, Wicked Stab (Rank 1) could be an option, but my gut feeling is that it is not enough damage per card.

The card draw aspect of Greyheart Sage can be replaced by Swindle or Dirty Tricks. Those don't leave a body though and don't corrupt Sweet Tooth, so maybe it's better to run a minion like Jungle Panther or Devouring Ectoplasm.