Honestly, I don't think relearning the differences between defiler and mystic will be much of a problem for me. I've been an mmo healer for 7 years, and I like to think that I catch on to playstyles quickly. I probaly won't switch at 80, I might switch at 70 or something, so that when I hit 80, I'll have caught on to those differences. My problem is *getting* there. I know that after 50, groups are going to be scarce. And I don't want to /wrists over my dismal bottom of the barrel soloing capabilities if I'm forced to. Also, soloing AAs I imagine would be a lot easier as a mystic as well, which is important to me.
So... I think I'mma make my defiler High Elf =). If for some reason you all are spot on correct, and I never get used to defiler 100%, I'll betray back to mystic lol. I won't be a gimped player if I can help it.