Now, now, the AI can be fixed, it just need to consider better it's moves when attacking. For example now when to retreat units, what units to be afraid of, to know which units are very vulnerable, to recognize weak spots, to anticipate the next likely move from the next player and to attempt actual strategies (ruses or attacking from different flanks).
Oh and get this, it has to learn to do all that and still be fun.. that's right, it has to be considerably smart, strong and merciless... yet stupid enough so you can win (odd, but the game must be fun and you can't give the player the idea that the AI is cheating either).
When you compare computers to humans, and the way we process information, computers surpass humans at doing one task really really well, whereas humans are exceptionally good at spotting patterns and dealing with multiple smaller tasks at the same time (and comming up with a creative solution when posible).
eg: google can be exceptional at finding a given picture if you imput all the necesary data, however only people can spot that picture from an image gallery. People are great at voice recognition... with computers you are shouting AGENT! AGENT! like a madman after 10 seconds.