I’ve been asked a couple of times the past week what the guild needs for raiding in Warlords of Draenor so people can re-roll a new class.
While this is all very good of you guys to want to do the best thing, my answer is and always will be, “Play the class you want, in the role you want”.
Ultimately, this makes you a happier player and better at playing your class because you don’t feel that you’re stuck playing something you may not enjoy.
The other reason I give this answer is that I don’t know what class balance will be like in Warlords, today’s OP class is liable to be the weakest class next expansion because that is generally how Blizzard over-correct things. So warlocks, brewmaster monks, blood DKs, enhancement shaman and disc priests will likely be the “ugly sisters” in Warlords as they’re the most OP right now.
The other variable is your guild, if the GM/raid leader tells everyone that asks to roll a mage or a rogue as they are the DPS class needed most right now, in Warlords EVERYONE will be a mage and a rogue and they’ll need a hunter, a warlock and a DPS DK to balance the team and then there won’t be room for all of the people that specially went out and rolled the mage and rogue, which makes them upset because they will claim, “I only rolled one because you said so, and now you don’t want me”.
If you’re really stuck for what class you want in Warlords, my generic advice is roll a tank or a healer as these are the spots most in demand. I won’t promise that you’ll be guaranteed a spot in yout guild raid team as they’ll only need 2 tanks and 2-6 healers depending on raid size and difficulty.
When choosing your class for your tank or healer choose one that has 2 alternative role choices as this means you get more flexibility. If you decide you want to try a tank role and you enjoy healing DON’T choose a warrior or DK. If you want to try healing but enjoy tanking DON’T choose a priest or a shaman.
Keep your options open and play what you want to play, after all it is a game not a job.