Dps warrior and rogue in high demand. Dont tank just spank! roll whatever u like to raid with. Whats the point of maining a class u dont like to raid with. Make alts for guild support like a healer n a tank but get the main geared!
Any healer has an easy time. Warlocks probably the least played of the dps and always in hand demand. Rogues and warriors are everywhere (though tank warriors are probably still needed for raids), anything else should be fine as long as you don't try to get a spot on an offspec. 0-1 slots for most of them, and half the population wanting to be enh or ret etc instead of healing so pretty much impossible to find a slot that way.