The lack of ships was shocking I'll agree, although the humans did have Gryphons and Gyrocopters so thats two air units.
Yeah both are pretty easily killed, but the same could be said of WC2 air units, hell a few Elven archers or Troll axe throwers would annihilate any dragon/gryphon. WC2 air units were only good against someone stupid enough not to have any archers/axe guys in a force. A mistake no-one made twice
Blizzard always do tough AIs, in this case they're very agressive at going out killing random map units while building up a base, which is harder for a person to properly - Hence the AIs advantage.