Air has many advantages - its fast, you can see whole map - best intel, its effective on places where you need it, but its extreme easy to destroy him, all what you need against air is 2-3 flak (320-480mass) and your army is safe against T1-T2 threat.
pillar (i all time comparing in UEF because think are first, and best balance fraction) pillar take another T2 units in 27sec, 15 pillars destroy 15 pillars cca in 27sec and cca 1-2 pillars alive. sky boxer destroy 1 gunship (gunship cost 40%more) in 6second, 15 sky boxers destroy 15 gunships in 0,5sec and 15skyboxer alive. 2 sky boxers destroy 15 gunships in 3,5sec and 1 boxer alive. 360 vs 2400mass.
Problem with flak is that its flak and has great area dmg, when air is coming in formation, then whiteout micro (what is hard in air) is losing all against flak with zero effectivity. Of course without effective anti-air units all will play only air and land will be useless, because air has many advantages.
We can compare mobile flak with static flak, what i do here viewtopic.php?f=42&t=3898 mobile is many, many and more time better.
In my opinion air would has strongest role in game and some (very bad) comparability with land anti-air units, and all it would be with less effective flak. When pillar (cheaper units) take 56dmg to another units why sky boxer take 3x this dmg, on 2x less armored units? Yes air has many another advantages but cheap units lock army against all threat and when static take lower dmg like mobile then its crappy.
I don't has any concrete suggestion, but think that would be good do something with aoe of mobile flak, and him crazy dmg.