As far as whats in demand....
I play a 67 Shammy on Bertox. From what i have noticed and from what i see on my server...
You see alot of beastlords and shammy's out there, not many SK's and even fewer rogues.
Demand means you have to have them....at high levels, you almost HAVE to have a shammy to slow, sure enchanters can do it, clickys can do it, but the shammy is a better alternitve to them all. Beastlords have crack and good pets, and are a great class i think. But when im starting a group and i am looking though the list of players in LFG, i dont go though the list and pick a rogue first ill tell you that. Sure they have the highest melee damage and if they are there, great, i like rogues. Are Rogues IN DEMAND...no, give me a mage or a wiz. As far as SK goes, same thing, they arn't tanks like warriors are. Although on my server there are some great SK's. But again..on demand? no. My advise is play what you want to play, all the classes in EQ have their strenghts and weaknesses and you can find a group no matter what class you are.