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.