Duo Leveling Class Comps

[Apatheist]

Warrior + healer (paladin or shaman) would be my choice.

Warriors are unstoppable with a healer supporting them. If you get ganked, paladins and shamans are both very tanky and freedom/dispels from paladins ruin anybody trying to kite your warrior. It's also generally fast to pug a few DPS when you want to do dungeon quests.

[Mercbeast]

Warrior + healer (paladin or shaman) would be my choice.

Warriors are unstoppable with a healer supporting them. If you get ganked, paladins and shamans are both very tanky and freedom/dispels from paladins ruin anybody trying to kite your warrior. It's also generally fast to pug a few DPS when you want to do dungeon quests.

At launch me and a buddy did Shaman/Warrior. Keep in mind that I was the 2nd shaman to hit the cap world wide, and he was like the third or fourth warrior world wide to cap.

It was a terrible combination. Neither of us had great DPS, anything that involved a lot of killing was quite slow. For classic I would not recommend a warrior + healer duo unless you're dedicating yourself to a lot of instancing and picking up DPS to pug.

Duo picks I'd put as top tier, would be, any combination of, Hunter, Shadow Priest, Warlock, Mage, and maybe rogue (rogues start off slow, and then become absurdly fast as they start to round out their abilities and talent points in an ambush build). To be fair, I never played my shaman as elemental, I was using a 2h'r and windfury to help my warrior bro get the most out of his abilities, and elemental shamans were objectively better DPS back then.

Duo shadowpriests can do things like, just run dotting everything and psychic screaming whenever the mobs pile up too much. Can do what are essentially enormous AOE pulls like this, even though you're not really using any AOE abilities.

(edit) Disregard what I said about warriors, I was under the assumption classic was going to be an early version of vanilla, not august 2006. I have no clue about the state of warriors in that patch, though my suspicion is that they are strong.

[Apatheist]

At launch me and a buddy did Shaman/Warrior. Keep in mind that I was the 2nd shaman to hit the cap world wide, and he was like the third or fourth warrior world wide to cap.

This seems to be a contradictory statement. If you were both top 5 in your respective classes worldwide to hit the level cap as a duo I don't understand how it could have been a terrible combination.

Warriors are killing machines that can grind through a ton of mobs non stop as well as tanking elites and dungeons in any spec. The only limiting factor is their HP, which having a class that can throw a heal every now and then, as well as provide useful buffs and DPS of their own will counteract. The more damage you take, the faster you can spam cleave and whirlwind. You don't want to go elemental on the shaman because you need your mana to top the warrior up. OOMing yourself every second mob casting lightning bolt defeats the purpose.

Anyway, when I refer to top tier leveling picks I don't really care about leveling speed. I'm talking about complimentary buffs, efficiency, the ability to do elite quests and dungeons easily and so on. Rushing to 60 is wasting the classic experience IMO. Though I think a warrior and paladin/shaman are still a lot faster than shadow priests or rogues. I don't see a reason to duo with warlocks, mages or hunters. They level faster solo.