Really nice game. I'm not sure if there was a patch to nerf the difficulty or anything, but the first few times I played it (yesterday) I got trounced and today I made it through all three levels. Maybe I didn't do as bad as I thought the first few times because I got overrun and didn't realize that even if you win you'll still get overrun but will beat the clock before the bird gets killed and have the enemy leader end up dead. That lack of realizing that getting overrun is expected might be making people think it's impossible even when they're close to winning.
I agree and disagree with previous reviews: there's a lot to understand about how the game works that doesn't get explained so the player sort of gets thrown into it and has to figure things out, but I think it's perfectly fine to make a game that way and toss people in to die for a while until they figure it out.
My only critique is the UI could have been nicer if the player could rearrange all the troops and trenches in the battle simultaneously instead of only being able to adjust one type of unit at a time and having to move back and forth to switch what you're adjusting (it was sort of a pain to rearrange troops to put heroes in the center of crowds that way).
Also are those percentiles based on actual performance of players? If so, maybe I'll play a few games with the bird thrown on the front lines to make everyone else feel better.