IRL tanks also have Point Defense systems and reactive armor. Basically the only thing that actually hurts actual modern day MBTs are dumb munitions like unguided bombs, hellfires and cannon fire. Those are the things that reactive armor tries to mitigate as well though there's no stopping thousands of rounds per minute from a Warthog or a Spooky. I think the only guided munitions from Close Air Support craft that can actually get through a lot of jamming from Tanks and their support vehicles are TOWs, since the missile is guided the from the source air craft rather than self guided.
We haven't seen IRL situations like this much. This is a super power versus super power situation and the closest we've seen modern technology combat of this nature is usually anything to do with Israel, or some terrorist who managed to get a hold of a rare guided rocket versus occupation forces. In real life, we won't use CAS that much, we will strike from precision bombers far higher up. There won't even be land units to provide CAS for because we will be busy launching high priority strike missions to disable the enemy before the ground conflict begins. This is why the normal General's credo is "He who has control of the Air, controls the War". We gain air supremacy, we win through air supremacy. Once control of the Air in establish in a sector we wish to occupy, CAS will cover land units and their logistics but Strike Missions will still be the power house. Air Force Strike Missions are like the new Hammer and Anvil of modern strategy.
On topic for
EoN though, air units here are CAS units. Not strategic ones. They will undoubtedly have counters since they are basically land units with no pathing restrictions. This is after all, a game. Nothing entirely accurate about it. Your mobility is yours strength, and the ability to run in very fast, strike from any angle is what makes air units so strong in any RTS/RTT. Hit and Run will be key, and Focus Fire will be the most efficient. Also, like what BorkBot mentioned, going Air is like it's own role, and in a game that is extremely team focused? It's better to go pure air individually and let one of your team mates go pure armor. With proper co-ordination and communication, the power you'll bring forth by going all-in with your army type will be far more effective than trying to be the Jack of All trades. Simply said? In team games you're not going to field and army for 1v1. This is after all, 20+ versus 20+.