Hunter has by far the most engaging rotation in classic though, if you're playing optimally. You pretty much have to install an addon tracking your bow shoots so that you can weave your aimed and multi shots into your rotation without interrupting your autoattacks, which compared to the 1-3 button 'rotations' most specs get is far more involved.
I do agree that the pve dungeon/raid content is the weakest part of the game though. I understand now why I was mostly focused on PvP back in 2005 whereas I'm a passionate raider in 'modern mmos': there's so much unengaging tank and spank, and even when the difficulty is there (well kinda, Drakkisath can be a bit nasty if healers aren't awake and Onyxia's aggro can be kinda hectic at times) it's just not nearly as much fun as a modern encounter like Mechatorque or Gul'dan.
If some version of 'classic+' ever becomes a thing I hope they don't listen to the hardcore classic fetishists who have convinced themselves they like 1 button rotations and fights that require no movement but a lot of consumables and decursing, because this style of pve is pretty boring. MC got popularly called 'the Molten Bore' back in vanilla, and it's twice as boring now with 1.12 class balance, modern game guides and faster computers.