technically, we don't know what spec is supposed to be for what anymore, as there were major changes with the expansion. What they are moving to, is all specs being viable for all types of play, depending on your play style. So while YOUR perception is a Demo lock shouldn't be able to out DPS another lock in equal gear, that's just your perception, and honestly is flat out wrong.
Quit thinking that Demo is what YOU want it to be, and look at it for what it is. You also really need to stop putting your perception out there as if it is fact. Because your wrong.
EDIT:
Ok, now that I have some time, let's totally destroy your idea that Demo is only for survivability and prove that it can be good DPS.
Let's look at the talents that help Survivability.
Demonic Embrace - Yes, Sta adds Survivability. However, it's also one of our main stats and used to add to our longevity. Also, being in the first tier, it is for all specs to take if needed, not just Demo Locks.
Fel Vitality - Same points as Demonic Embrace really.
Soul Link - Yes, this is survivability, however, it's been nerfed. It adds some, but not a lot. It was also moved up in the tree so that it could be accessible to all Specs.
Demonic Resilience - Ok, resilience, yes, a PvP stat, but it also adds to our pets survivabilty so he can stay alive in boss fights.
All in all, yes, there's some survivability there, but it's all low in the tree in order to be accessible to other specs, not just Demo.
Now, let's look at what Demo adds to Damage:
Demonic Brutality - Felguard Damage. Yes, it adds to VW taunt, and makes soloing elites easier too, but the main reason a Felguard spec takes it is increased damage.
Unholy Power - All about pet damage.
Master Demonologist - Yet more damage.
Demonic Knowledge - Spell Power = Damage.
Demonic Tactics - Crit, more damage.
Demonic Pact - Raid Damage Buff.
Meta - Armor yes, but ask a tank, Armor isn't what they look for to be more survivable, they want Defense and Avoidance more. 20% Damage bonus, extra trinket basically.
So as you see, as you get deeper into Demo, the more it improves your Damage.
In Summary, low Demo can add Survivability to an Affliction or Destruction Spec, but deep Demo yields some excellent DPS.
Edited, Dec 8th 2008 11:30am by Lathais