well the thing about demo is that most people don't use it, I've seen a demo lock pull 5k dps in ICC10 on a rep run but as far as that goes that the only time I've seen a demo lock do any good. Most people prefer Destro because of the fact that it is awesome burst damage, affliction is not as reliable because of the debuff cap that each player can have on 1 target, afflic however is good for multi target because you can cast all those buffs on more than 1 target.
