Yeah, TBC was the best in terms of PvP, but then again, i just started with wow in the middle of s2 and i happen to be a warlock, too.
created later a rogue and mage and what can definatley be said, is, that TBC was the best pvp addon for pure DD classes, they did the most dmg and burst and the cc was more of a big deal, too.
Could also say MoP and WoD were good PvP expansions, but in MoP, while a fresh class design that actually worked(unlike legion) people stopped to die, but then again i played a Hdruid which were ridiculous with symbosis, kinda adding another def cd like pala bubble or mage iceblock to my my own arsenal of immortality.
And in WoD stuff died quickly again, but there was that nasty pruning.
TBC got it right, arena felt fresh and new, too, no balance around healers or 3vs3. And most importantly random bgs did reward you with actually good gear for your effort and time and it lacked disgusting bg design, isles with machines and other distracting nonsense. ;>