I would caution you against running LFD / mythic dungeons with 2 pub DPS. In fact this was my biggest stressor during Wrath as you'd get a number of morons. Once they realize you play all 3 they cry, moan, try to votekick you (lol) and a whole lot of pulling trash to wipe your party.

The WoW community is extremely toxic towards multiboxers as it's seen a form of class envy. I 5 box to avoid most of these people and still they occasionally find us in the open world and /spit, cry more and generally try to be as much of an asshole as possible. This is with war mode off not bothering anybody. And LFR.. lol. You can top all the meters and be the MvP of the group and they'll still vote kick you. Yes, even if it means costing them another half hour. Not a very intelligent group but it is what it is.