AA needs allot of help atm.YOU THINK AIR UNITS ARE CHEAP? im being serious.
Its quite useless once a horde of air hits you.
The main problem is that air units are very generic and good against everything.
They are cheap, one of the fastest units, can go across any terrain and attack any unit(even aa).
There should be a serious tradeoff to offset the "good vs everything" quality of air. ( especially on larger maps ).
AA can't attack anything else and is completely useless unless it fights air. This should give it a certain number of guaranteed kills against air.
E.g like in real life, it should fire and forget its missiles and be able to retreat. 1 missile = 1 downed banshee/hornet.
So that a single aa can still take out 1-2 air units, even if there is a horde of them and they kill the AA unit in a second.
It should also gain a splash damage through an upgrade.
In general, having AA on the battlefield should be a strategic unit that air players should take into considerations.
Right now, I've spent my entire pop-cap on building reavers to fight against air players( who I scouted and knew in advance were building only air), and lost miserably.
A horde of AA couldn't take out a horde of air which it should...effortlessly since its a hard counter to air with no other purpose. AA unit, in general, should be a unit that is not built in masses.
You can also see if some units are OP if you see players only building 1-2 types of units and winning.
This is getting quite boring in my opinion.
I like if players play with many different units, especially infantry mixed with vehicles. This just doesn't happen that often.
Infantry = good players > early game > few snipers + lots of anti-building units > rush for minibuses
In mid-late game > everybody > full pop cap of air OR scarab with rest of the pop cap spent on useless reavers. No unit mixes.
Of course, they are cheap,
Considering that they dont have a real counter and they can attack everything...while many units cant attack them at all means that they should be more expensive...or have a real counter(AA that guarantees a kill on first sight - fire and forget - one shot one kill - slow reload )
Air should be a support unit - may be something like Command and conquer air units - where air is meant to take out strategic targets/bomb unit clusters and fly back to base for reloading.
Air in C&C is expensive, has high damage but is also very vulnerable to AA. In C&C if you run into AA then you can be sure you will lose at least a few air units even if you take out the AA.
That's how it should be.