Thanks for your thoughts everyone,

first let me get this straight: I am just fooling around with the idea, I am nowhere near actually trying it! Of course there are fights that may be rather easy (Attumen, Kurator, Chess ) and some fights that are virtually impossible (Nightbane ...). But the announcement that in Wotlk all raids will be 10-mannable made me think...

The basic problem seems to be diversity of characters vs. synergy. What good is an ability of a character if I cannot use it due to me being occupied playing the other 9 toons.

This is the reason I didn't include a lock in my strategy. They can do nice damage but other than that I cannot see much usability to the group. Soulstones are not necessary because of ankhs. Healthstones are nice in theory but in my experience the micromanagement is too much if you try to use healthstones other than on the MT. Am I missing something about the lock? A core ability I am not aware of at the moment?

The second thing whould be the tank situation: I think everybody can agree on a paladin MT. For fights where a second tank is needed one might suggest another paladin. The downside is, that that char whould be "dead meat" in fights where only one tank is necessary. So basically I want a second tank that is somewhat useful in fights with only the maintank in action. I figured a druid could just switch to his caster gear and whould blend in with the mages/shams an be in "fire-and-forget" mode till needed for tanking again. In my opinion the druid is much better for that than a paladin (or even a warrior). Or is the paladin so much easier to tank with (read: requires so much less attention) than the druid to make it worth having a second?

What about a hunter? Does he bring any utility to a group that is based on magical range damage (besides dmg)? For purposes of 10 mans I like to ignore the off tanking pet.

More input please :P