To be fair, Engineering is the highest skill ceiling class in Vanilla PvP.

The fact that Rogues get so much credit for having a high skill ceiling in Vanilla makes me wonder exactly who responded; the class can be tough to grasp at first, but once you know your partial/full CC rotations, the difference in damage output vs. different classes and their gear level, it's a class that doesn't need to react to as much unpredictability as their opponents since they often dictate the engagements.

They look impressive when they disable you, but they're no Elementalist, Druid or Warlock. Hell, even Hunters are harder to play given how many bad matchups you inherently have. It's the weaving in of Engineering gadgets that makes Rogues look harder to play than they are at their core. Until Shadowstep came around, Rogues were way overrated in terms of difficulty. It took until Arena for there to be a massive gap between talented and average Rogues.

For all one might dislike Arena, it added so much micromanagement demands that Rogues started needing a lot more work than their Vanilla counterparts. That wasn't true of every class, but the skill ceiling of Vanilla Rogues is nowhere near that of some of the later expansions.