I know that when Jer and myself run three accounts (one of us is DC'ing) on a raid, we can get massive amounts of lag. We /cmd filter 1 0 ... it relieves a lot of lag on raids, not sure in exp. groups / dc situations.
As far as combos go that are easy to do, I don't know which one you would want. I'm a big fan of melee / healer. But at this point the game is just littered with melee / healer combo groups. I've seen Kimmy / Kimmie, which I believe if I remember correctly is a mage / wizard combo. I have no idea how she did so well, but hey, if you're a good player I suppose you can make anything work. Root, send pet in, nuke. Meh. I'd just be worried about the pet taking too much damage and dying, which would seem counter productive.
Oh, another combo I've seen that works really well is Mag. / Shaman. Slow with the Shaman, send pet in, dot with Shaman, nuke with Mage, heal with Shaman. The only real problem I see would be having some adds. How to get the pet to tank the adds would be difficult. But with Shaman slow, anything is possible.
So I guess it's pretty much up to you. The high end needs more int. casters though, that's for sure.