Windy Hills is a tricky one. Short and brutal, it'll demand you a lot of things, and not just a specificly designed deck, but a specifically designed deck including Skill Cards.
It has 2 stages, the first being very streightforward. Stage ONE is NOT equialent with Stage TWO, do NOT try to solve Stage 1 with a Stage 2 deck! Stage 1 requires your usual boss-killiing deck, whatever that is. The boss there'll release tengus and whatnot, almost having the same deck as for Stage 2, but there is a rather important difference: stage 1 has no tricks, everything starts from across the plain old field. So you just have to bring stuff to massacre everything mercylessly - and the occasional lifesaving / lane upholding stuff.
Stage 2 is where the real problem lurks. It starts with big heroic tengus in your face. That's the BIG problem you have to dispose of right away. Use Backstab primaly, Vigilance secondary.
Greenears tend to comit the mistake brining squires and such 1/5 vigilance stuff here - that won't cut it. What'll cut it is Backstab, well-placed Vigilance units - Whirlwind prefered above that -, and direct damage.
Try not to use up all your direct damage in this part, it'll come in handy a minute later. Try to place Vigilance units in a row what just got rid of the heroic tengu (to not die at first strike), or at place where it'll kill the tengu directly behind it with its first hit.
The level on the AI's side mostly includes tengus, what means flying creatures. They mostly have backstab, and like 1/3 of them have heroics. 1/3 of the whole army is made of Feles, what means Ability: Ambush.
Special units are Mifzuna the Wind who can end up in your first pods right away, but hopefully gets stuck along the way. Hafnaar is REAL MESS sending all the enemy horde filling your spawn-pads in one turn. And there's a totem boosting the damage of all enemy units, but hopefully that won't be too high of an issue.
Hafnar is trouble, because the AI after 1-2 turn you disposed the initial tengus will play out its whole deck (what is not humongous) in just 2-3 turns. You must prepare for this. Hold your cards, fill key positions, and prepare that despite all your efforts most of your spawn-pods will be filled anyway. So Direct Damage is a MUST, to be able to kill Hafnar, the tower and key positions of your spawning places imediatelly.
Deck to bring
15 card deck, no more.
Preferably lots of backstabbing tengus with high damage: Tengu Bloodseeker, Tengu Assaulter are most welcomed. 6-10 cards.
physical immun things (desperate soul, dread wraith) x1
Wind Dancer Elke is nice, but anything with wigilance and low charges.for emergency is welcomed. This probably means human and undead units. Used for emergency-purpose mostly.
Healer: Things like Blessing: Armor or Cure have no place in this battle. The only thing a Healer should have is Sanctuary and Refuge. This later is problematic to use though, but is an attractive idea.
Mage: Armageddon can clear the entire battlefield in one go. If you have it - you'll be praised for it.
Ranger: Disturbance and creature-removing skills are suggested.
Any single hit direct damage skill is welcomed up to 3 cards in the deck.