When I played priest during vanilla, I didn't need a full bar of heals. I only needed Heal rank2(or lesser heal rank2?). There was never a need to heal for more, and it was by far the most efficient heal.
Still there was some skill involved for some roles on some fights. Not much more or less than I assume in current wow though. Picking up adds, moving shit where it has to be tanked, timing your zerker rage for fears(unless you were alliance), it's not overly complicated stuff but it still needed to be done well and at the right time, which is how wow works.
I mean a lot of people swear by Dark Souls' difficulty and shit, but ultimately Dark Souls is a game of knowledge where once you've mastered patterns the only thing that's left is doing what you're supposed to which is mostly dodging/block hits until you have an opening, hitting once or twice, then going back to defensive mode and repeating this over and over. If you've played Dark Souls multiple times, chances are you found the game very easy on the 2nd playthrough even if you picked a weird character style and even more so if you played something strong. My greatsword playthrough of Dark Souls was my 3rd or 4th and I only died a few times the entire time because of how easy everything seemed when I knew exactly what was going to happen.
WoW uses the same systems, once you've learned a fight it's just a matter of executing your own role which is simple enough, one fuckup often leads to death(and in wow often to a wipe, but not necessarily, depends on the death). WoW has the added layer of having multiple people performing the same fight increasing the chances of fuckups. I don't think the challenging wow stuff was much easier than Dark Souls was, there was a lot of randomness in patterns and even with the DBM calls and shit, it only told you that something was about to happen, reacting appropriately was still a split decision.
It isn't the difficulty and skill requirement of playing a twitch FPS which needs much higher reflexes and precision, or playing SC2 which requires much more intensive micro and macro, but I think Dark Souls and WoW(and modern mmos) are fairly similar in playstyle, minus the multiplayer aspect. I think for many people who played Dark Souls a decent bunch then player Dark Souls 2, it's fairly apparent that Dark Souls was only truly hard because you didn't know what to expect. In DS2, a lot of the fights being similar to DS1, the game appeared to be much much easier than the original, because you already knew the patterns and how to execute. I feel that's also what happened with later wow, people got used to raiding and while the encounters had new mechanics, at the end of the day it was more of the same skills being used and if you had been raiding for years every week, adapting to a few new mechanics wasn't hard enough which led people to feeling like raiding became easier, when really it became harder over time(at least in hard modes once they started splitting). If you look at it objectively though, hard mode pandaria is probably 10times harder than anything ever made during vanilla and BC, other than broken content.
Anyway saying wow doesn't take any skill is either hyperbole or simply stupidity. Everything takes some amount of skill to varying degrees. You might say it doesn't take enough skill to challenge you and that might be true, but for the most part it requires a decent amount of skill, with the main issue is that wether or not you have enough skill doesn't matter in your success or not entirely, since you also need many other people to have the same amount of skill and all of you need to perform perfectly at the right time. But I'd say it takes more personnal skill than a lot of other games because it uses similar concept as Dark Souls, you have very little time to react to pseudo random events(you know something is coming, and it might be one of two or 3 things) and reacting badly almost always results in an instant loss. The skill requirement is mostly applied through the extreme result of failling to do simple tasks, rather than executing complex tasks.
