Well look at it as if they were temporarily given the use of a special object to defeat hero xyz. Perhaps their council or leader, whatever granted them one just like we are once in awhile granted a special power. Like the poster above stated the AI is at a disadvantage facing a player. I find it very rewarding defeating a villan after dancing all around trying to stay alive and winning. I find it a major rush when i'm all up on inspirirations and endurance is down and health in the red while standing over the fresh bodies of my foes! So no I do not think that villans using powers I don't have access to is a problem.
