To add on to Hairball's list...(I don't have much experience boxing in naxx yet, so some of this is just theory)

Spider 2nd: have the DK tank the boss and dg adds when needed. If you don't have a DK tank have a DK dps do it. If you don't have any DKs then move the boss to the adds, not the adds to the boss. The adds like to cast instead of moving.

Military 2nd: Just make sure your team is all on the same side. You can also just have everyone stay on one side, but if you're still gearing up that probably isn't a good idea.

Military 3rd: In 10 man you don't need insane DPS to burn thane without swapping.

For Grobulus, an all ranged dps box could probably do it by just moving the one that gets diseased away but if you're doing multiple things that gets a lot harder.

Gluth is pretty tank+spank, I don't see him giving anyone a major problem for boxing related reasons. A 10-boxer might have problems but as long as you aren't the kiter it's 100% tank+spank, and if you are a kiter you just have to kite while mashing your dps/tank macro.

When I was thinking of how a boxer would do thaddius I came up with an easy way to 3-box it. You need a way to move all of your characters forward, a way to move any single character forward and backward. If one gets switched just move that char, if two move everyone forward but hold backward on the unswitched, and if three just move everyone forward. You then just need to turn the people who got switched, which can either be manual by mouse or using the same methood with turn left/right instead of forward/backward. Any more than 3 and you'd have to have a move forward and turn for every individual character. How many you can bring is limited by how fast you can react to charge switches. For the jump you can do every character individually, get a levitate/slow fall, or follow someone else and broadcast your jump. You could also have two different jump buttons, one for main and one for followers.

Saph is probably easy. Tank+spank+move out of aoe, then spread, then come back together, repeat.

KT is all about watching out for void zones while staying spread out.