It can be somewhat difficult to spot because it's hard to tell when the AI will attack with what at all, but it doesn't seem to factor exalted into calculations well enough.

For example:

It has 3 creatures with exalted, all with 2 power and 2 of them evasive because of protection from black.

Instead of attacking with one pro:black guy for 5 damage and having the other one available to block, it will attack with 2 pro:black guys for 4 and leave itself vulnerable to attack.

Or a simpler example would be that if it has 3 Aven Squire it will attack with all 3 for 3, instead of just one for 4. Or if it has 1 Araba Mothrider and 2 Aven Squire it'll attack with all 3 instead of just the mothrider for the same ammount of damage, etc.