In some ways, this makes Ishamael/Moridin a more pathetic yet sympathetic character. Perhaps that is why Rand carried his body out of the Bore.
I suppose there is an esoteric precedent that in a mirror world, it is possible for one of the Dragon's to fail in the task or choose differently, but the Prime World seems locked into it's course with many internal systems of correction to prevent anything else from happening.
I'm open to any other ideas, though.
Personally I sympathize with Moridin. The way RJ set up the wheel of time, everything seems so pointless. Ages repeat over and over with the same result. Free will is most definitely an illusion, considering the nature of ta'veren and how the wheel makes course adjustments.