Have you just switched guilds or are you still in Happy Rainbow? I only ask because I looked through the armory at some of the other locks and believe me, you are not the problem in that set-up. One of your locks has King's Defender
(http://www.wowhead.com/?item=28749) equipped! What made him do that? I'm not flaming for the sake of it, and some look like they've logged out in PVP gear but still I'd be surprised if they aren't under-performing.
As for you, I'd say you're doing as well as you can. Affliction DPS is naturally lower. I checked mine on the spreadsheet and currently with my 21/40 build it's 1797, with a respec to affliction this drops to just under 1300.
You could ditch some of your +hit gems but if you run BT/MH every week then sooner or later you'll get upgrades that don't have any hit at all so it depends how much you mind re-gemming. I always feel a bit bad about destorying epic gems I've invested in.
I'd also drop Siphon Life from your spell rotation for boss fights. It's negligible DPS and just a waste of the GCD.
And if your guild still think you're underperforming remind them you're there for utulity and point them to these forums to learn mroe about the different roles of warlocks.