A lot of it is because the 1.12 talents for mages are ridiculously bloated and broken. I mean, they get 6% spell hit for 3 points on their first tier, that should show you where this is going. While strong, Mages weren’t nearly so faceroll through 90% of Vanilla’s lifecycle.
Mages are broken in PVP for two reasons:
Why does a Rank 1 frost spell have any slowing effect on a level 60 whatsoever?
Why does frost nova affect everyone on the entire team seemingly at any range?
I have to pee so much IRL while playing my mage because his constant drinking, he stops to drink I take a drink, 5 minutes alter I’m saturated with Beer
fight, drink , blink to catch up to tank kill the mob hes been hitting the whole time i was drinking and is still at 90% health repeat
Because they have high and reliable damage + high mobility and survivability + easy AoE output + good control and utility all on the same character. Who cares if they have a hard time with some classes 1 v 1.
Warriors struggle 1 v 1 (especially w/o FAPs), too, and nobody would suggest they aren’t one of the dominant PvP classes in Classic.
Warlocks, Spriests, Hunters, rogues, etc, are all much more vulnerable to focus fire trains or being locked down than those two classes.