In reference to your location, you must be doing some Lord of the Rings style quest for coffee.
In response to your post, I'll say that even at maximum level, I find myself with a huge multitude of spells that, sure, I know what they do! But I don't know how to play efficiently. I'd say that comes with time, with practise, and with a little bit of study on even the basic guides on Icy Veins. Of course, common sense does play a part, and a boosted character to 90 will be in the hands of
a) Someone doing Raid Finder, where even a rudimentary knowledge of the class mechanics will usually provide adequate performance.
b) Someone doing actual raids, who will 9/10 look into actual methods of learning their new class.