I've been reading through the forums and didn't find any information about this that's not outdated (probably) at this point.
Are there any classes in general that are in high demand and is there any lack of tanks or healers in general ? I'm new to the server so I'm considering my options.
There's always lack of tanks and healers. As for DPS; boomies, shadow priest, locks are mostly in demand.
If u go tank, make pala or dk, noone wants war or Bear.
As for healers the most desirable are ShamyPala > disc rdudu > holypriest or so.
As for dps, lookc up some general wotlk raid comp guide or something like that, see what dps is desirable due to what raidbuff / debuff and just go with one of em.