1) AI anti-air capabilities are weak. In skirmish matches 4 Kirovs have no problems with going the heart of the base and taking out the ConYard against Mental AI. On smaller maps it becomes more visible.
2) AI do not include at least 1-2 serious anti-air units (Aeroblaze, Oxydizer, ..) in their attacking parties. Thus they got destroyed by Wolfhounds, Balisilisks or Thors fairly easy.
3) Thors and Wolfhound are clear game-changers. Thor eliminates infantry almost instantly, multiple targeting makes groups of anti-air units virtually useless (even Wolfhounds). Wolfhounds in packs render most of vehicles useless.
4) I see no difference between Easy, Normal and Hard difficulty levels in terms of initial forces (yours or enemy), initial credits, additional tips or avalable powers or additional revealed regions.
5) Saboteur groups a far more effective defense destroyers than tanks of the same cost. Several nuke explosions can create a weak point without a notice.
6) Shouldn't some infantry units in closed costumes (like Desolator, Tesla Trooper, Pyro, Siege Cadre, Chrono Leg., Stalker, Rahn, Siegfried) be immune to poison? Poison annihilates heroes in seconds, not to mention standart units. Molebombs are anti-hero panacea.
7) Nuwa is absolute annihilator.
In overall, I think that most powerful units must have reduced building speed and slightly higher cost in order to contain spamming and do not have production bonus from multiple factories for them.