I have a set at 70. They're still 70 because with the post-3.0 melee dominance and squishiness of shadow priests, it was an all or nothing proposition. I'd either one-shot them with mind blast x5 or I could hardly dent them and went down fast. Having to shift out of shadow to do any healing killed the 15% +dmg & DoT crits. Combine that with never having enough dot uptime to regen mana with VT and the old version of the warlock shadow/fire immunity and they just weren't attractive to me anymore.

Plus, they sucked at elite quest mobs/dailies versus just about any other group I've played. The way I think of them is sorta like affliction locks with no pets.