I have a group of 5 shams at 70 as well as a holy priest. I have always played with the idea of 10 boxing but never really got around to doing it for several reasons. I recently decided I will give it a shot for wotlk (ofc inspired ny nixi). There will be so much more to do with a group of 10 in wotlk than in bc (basically only kara). I thought about it for a while and decided to level 5 more characters on the same accounts and later transfer them to 5 new accounts. My shams run the fast 6 sso dailies to earn money (~300g for 30m every day) and the rest of my (limited) time I level my new group. I try to make as much money and get all tradeskills for all toons to 375 to be prepared for wotlk. I also collect herbs and leather as I level up the new groups gathering profs to be ready for a char to have the new profession.

As for the composition of the new group I went with:
prot pala
heal pala
mage x 2
lock


Add to this my already 70s:
4 sham (1 will be ditched)
1 healpriest

and I think I will have a decent group. It is almost the same as nixis setup. The heal pala is going to be my second tank for the fights where one is needed; one sham has to heal if that is the case. I considered adding a driud for motw and tanking/healing capabilities but decided not to. One of the advantages of the new group: all are be and could be started in the same starting area. The new group is currently lvl 14 but is going to be a lot of fun when i get into the 20s due to its aoe capabilities.

Anyways, if that doesn't work I ccan always add a dk or two or three....
Bunny