gratz man thats awesome! I can't even imagine how long it took you to level 20 characters to 80, be careful, Sam may put out a hit on you!

You should DEFINITELY step into Ulduar this week. oo, except the vehicles have reticular targeting instead of target-by-mob, that may be difficult to multibox due to needing to use the mouse to target more or less, at least for trash clearing. Dunno you'll have to try it out and see how hard it is to multibox.

Razorscale will be a bit tough to multibox, but not impossible. You just have to be really, really good about moving out of puddles of fire on the ground, tanking/picking up all the adds, and firing harpoons at the right time. Will require some coordination. Can totally skip.

Ignis may be not worth it, its not a super hard fight but not really sure how you'd handle all the targeted-healing (flame pot), OT moving adds to specific spots, and 1 DPS taking care of adds. Could be doable but will be a lot of wiping, lots of trash too that takes a while to clear. Can totally skip.

xt02 will be relatively easy, you can single tank the boss up on the stairs, have everyone spread out a bit, not sure how you will deal with adds however - 4 shamans could theoretically take care of them all with magma/earthbind/flame nova totems, but you still have to deal with constructors and adds getting too close. gravity well is also an issue, but you can tab quickly and move away i'd think. The adds will be the hardest part of this fight, will need to figure out a strat to deal with them - fwiw I am able to kill all the (non constructor) adds as a mage in 10 man, but I have to move around a lot and thats all I really do.

Kolgarn may be hard, not sure. Its a relatively straightforward boss but need quite a bit of rapid-healing on random targets, and one person is constantly targeted by beams (ala grobbulus) and has to move. If you maybe DPS both arms down quickly you can make this an easy fight.

The rest of the bosses (Iron Council, Hodir, Thorim, etc) however I think are going to be insanely tough to multibox, there is just too much raid damage, movement, and tank swapping to easily single box them.