So before we get into what I mean by "WoW skill", I want to concede some caveats:
• I'm talking PVE here.
• Gear is more important than skill.
• Raid success often has more to do with organizational effectiveness and group dynamics over individual skill.
Now that we cleared that up, I want to address what I think has been a massive shift since the beginning of the game. And for me personally, not something I like very much. Early on in Vanilla, boss mechanics we essentially laughable, but classes were far more complex. Skill leaned hard on "knowing your class" over "knowing the boss".
What I really liked about this is if I was a veteran X class, I could enter any boss fight, learn the few mechanics, but my skill and knowledge always carried over from fight to fight.
Now it seems like every spec is extremely easy, but every time a new tier comes out it becomes exhausting to have to learn every mechanic for every boss (and sometimes multiple phases). It no longer feels like I'm mastering my hunter, it just seems like I'm mastering a temporarily valuable boss fight.
Nothing carries over either. I could be the best X class, but it doesn't matter if I don't know the boss mechanics.
I don't think it should lean heavy either way (but def slightly more towards class mastery), and I do think you should be able to pick up on certain things happening in a fight and as a veteran player know how to handle it on the fly, just by your knowledge of the game.