There are those guilds out there that welcome multiboxing dps in their raid. Its all about knowing the content, my best advice is to run it a couple of time with a solo character and prove to the guild that you will manage it.

I run at the moment 5 dps in our main 25 man raid team and run either 3 dps or 2 healers in our 10 man group. And so far the raiders love it. And I dont feel I lose any dps from it, sometimes its the opposite. They gain more by having a multiboxer with them.
As a multiboxer you are more used to pay attention to the enviroment.
So keep searching , cause they are out there