Vividly remember being able to kill players 8-10 levels higher than me if they were awful on my warlock in vanilla. Also vividly remember groups of lowbies being able to gang up on higher levels without all of them having to be melee.
I've had moonfires, roots, and faerie fires completely resisted at 60 on extremely rare occasions by level 20-40 players, while leveling I had absolutely no chance to root or land anything on someone orange +, which I understand is intended in some sense but it just seems off.
I don't have the math to back any of this I don't know if there was a default 1% chance to resist (don't remember that being implemented in pvp), but pvp spell hit rating does seem funky.