air.
needs.
creatures.
We have 4 + 1 dragon + 1 nymph.
fire can pump out stuff with cremations, has two creatures with 7 attack and 5-7 cost, has explosions, do you guys really need any more stuff?
water has perma, a nice buff for squids, two creatures with 6 attack and 4-5 cost, congeals...
Air definitely could use another creature, but you are missing Animate Weapon + Owl's/Eagle's Eye in your creature list, which is probably Air's best creature. Air is actually the only true mono I like to run. I think individually it is one of, if not the single, strongest element. Two great shields, Owl's Eye, creature generation, Diving Wyrms/Sky Blitz... It's a versatile element. Definitely my favorite mono to play, so I don't think it's at the top of my list for needing a new card.
Fire is one of my other favorite elements, but the problem with Fire is not a strength issue, just a game issue. You could literally put *all* of Fire's cards into a deck, give it an Earth mark, and actually win games. You can mix and match any and all of its cards. There is almost no interesting strategy, because all of the cards are individually playable. Fire doesn't need a gamebreaking card, it just needs diversity. Fire is strong, certainly, although it has become slightly weaker as every other element has developed and diversified and it has stayed stagnant. It doesn't need a new card or two because it has gaping weaknesses, it needs a new card or two because it's kinda boring.