Meh, I was starting to write something, but then it just became a mess.
For the moment, this one server system looks fine to me.
I'm not into big raids (I think its high time devs move past the whole raid mentality, it is not fun and becoming too elitist in most games), so having smaller groups of people doesn't bother me.
I guess we'll have to wait and see what Cryptic has planned for the big stuff once you reach the level cap.