We usually raid with 4 warlocks and just about everytime top dmg dealers are locks, trash and bosses... Occasionally a pala/hunter/warr is there aswell, but none of the mentioned come in those positions on a regular intervall...
1) If the person knows how to play his/her character and can maximize a lock's DPS output no matter what spec he/she is using, then that's some SICK DPS right there regardless of whether it's 1st or 3rd or 5th on the meters.
2) What RL does not want at least one SS in a raid? Seriously?
3) And for the lazy people who cannot even click a release button, there we are (warlocks) to summon their butts back into the instance. I mean do you know how much time Warlock Express saves in a raid?
4) I dunno about the rest of you, but my guildies just LOVE my awesome healthstones. They really do! ;D
As long as you can fill those 4 roles and come equppied with shards, then I'm pretty sure you're just about (if not MORE) as valuable as a ffb mage with a table.