None tbh.
WoW is just a game, recommended for 12+. Each classes have certain amount of abilities, and it increases while your chars levels. And totally amount of each class's abilities are roughly the same. All you need to do is to be capable to read the tooltips and use them at the right time.
i dont think using 30 abilites at the right time is much much more skillful than using 20 abilites at the right time. No class require significantly more skills than others.