When it comes to vanilla, PvE is always better on Alliance.
Trying to level Alliance on Elysium is one of the worst gaming experiences tho, second only to playing League of Legends.
What is actually driving us away from Elysium are lvl 60 mongoloids from <NOTHING PERSONAL> camping lowbies in Arathi Highlands for hours on end.
I'd tell you to take it to battlegrounds if you're interested in PvP but we all know Horde gets bent over every time they actually managed to enter one.
Warlocks need gear to perform. They suck dick in early vanilla and become godlike in later patches. I wouldn't bother playing one with the gear that is currently available.
Mages are always good.