[Snake]

That's just a staple for utility and defensive skills outside a few which are reliable or tied to heals TBH.

For short, I believe Valley Gale could just reduce non-martial attack's damage by a flat amount equal to 50% of your Wind ATK, or deflect all ranged attacks up to 10% of your Wind ATK times, rounded down, while consuming one feather per deflection.
The Guard on it could also be more special, in a way it doesn't reduce Evade. You're using resources to cast it, including all of your precious momentum. In Fate/Stay Night terms, Lancers are the hard counter to Sabers and Archers, so it's not -that- farfetched from anime memes, and for Firebird itself, having a 'Guard' skill which basically roots you down, when you're an acrobatic lancer is a little odd.

Nest Flight could easily be similar to Retreat Flight from Ranger, where you attack one enemy then backflip away to gain an evasive bonus. It does look like a disengaging attack, so it could easily just perform an AoE swipe attack that attacks all cardinals similar to Axe's Special Attack, then have you leap backwards as long as the last tile is empty.

Burn Away should be able to be used by yourself, yes. Maybe also provide Frozen and Immobilize immunity as a bonus for damaging an ally. You're toasting their fine cheeks, they should get hippity-hoppity enough to shake off both of those for a bit.

Roaring Falcon shouldn't increase Sound ATK of allies, it should increase SWA, since that is better used by allies than not. I don't think the SWA should apply to yourself, if that becomes the case. For obvious reasons.