This is old but I’d say:
Alliance:
Night Elves = Druid/Rogue
Human = Rogue/Warrior/Paladin/Priest
Dwarf = Hunter/Paladin
Gnome = Mage/Warlock
Dranei = Shaman/Paladin
Horde:
Troll = Hunter/Caster/Rogue
Orc = Warrior/Rogue
Tauren = Druid/Shaman
Undead = ??? Don’t know
Blood Elf = Paladin/Caster
Just play whatever the F$%^ you want, at the end of the day unless you planning on going pro, this choice will not matter at all since an average level of gameplay will get you through all the content and will make you play well in PVP. Now if you want top arena ranking and be the best raider in the game then alright, follow the meta thing.