Lets go through for each race and pick an iconic class.
Classic races:
Alliance:
Human: Paladin. Gotta be paladin. Arthas, Uther, Turalyon, and more!
Dwarf: Warrior. Mountain Kings, baby. For Ironforge!
Gnome: Warlock. Because there’s no Tinkers, but this people prone to remarkably bad decision making? Definitely the most likely warlocks.
Night Elf: Druid. Do i need to explain this at all? I love Demon Hunters and think they’re iconic, but they’re not Perfect Examples of the race.
Horde:
Orc: Shamans. Thrall, but also their entire religion being shamanism. That it plays such a huge role to their society. Second choice would of course be Warrior.
Trolls: This one is hard for me. I’m gonna go with Priest because i think most Witchdoctor stuff tend to use Shadow Priest, and i think thats the most iconic.
Tauren: A left field pick of Hunter. A big part of Tauren culture as we were told was never wasting, using everything they had. They didn’t quite have a Nelf worship of nature, but a respect. I think hunter fits well with that.
Undead: Rogue. I dunno what to say. Undead rogues are iconic more for having played Classic than for any specific character to me.
Wow, that was quick. Now onto expansion races:
Burning Crusade:
Draenei: Paladin again. Sorry, i know their racial leader is a priest, and they were literally introduced to allow shamans on ally side… but its Paladin.
Blood Elf: Warlock, at least originally. The fel addicted elves making use of fel magics and fel bargains with fel beings? Yeah. Of course. Nowadays i lean towards Paladin for these guys as well, though.
Cataclysm:
Worgen: Worgen is a hard one to pick for me. Is it Warrior, for the fury of the beast? Is it Hunter, for the werewolf and their wolf pack? Is it Death Knight so you can be a vampire werewolf? Yeah lets go with Death Knight.
Goblin: Warlock. Same reasoning as Gnomes, except you know their contracts are more abusive towards their demons.
Mists:
Pandaren: …It’s Monk.
Dragonflight:
Dracthyr: …
If you want to see me break down the allied races uh. I probably wont. I dont think I know much about any of them. Or care.