They are/were WORLD CLASS though.
Sorry, I stopped reading there as I don't think you understood my point. They weren't always world class- they developed into world class players. Rafa obviously thinks Babel can be world class- he spent £10m on him which is a lot for a player of his age/experience. Babel (and the others before him) won't/didn't develop into world class players by having all these defensively minded duties when they're young confident attacking players. Babel came here with confidence, and it's all been sucked out of him. In order for him, and any other such player for any other team, to develop their talent to a top level of football, they need to be developed in the right manner. I think Rafa's had massive success developing midfielders and defenders (Agger, Skrtel, Alonso, Carra, Arbeloa, Reina, Sissoko, Mascherano, Gerrard (his more defensive side)...) but not so much with attacking players. And I think the reason for that (as I've said in another thread- possibly the Level 3 one) is because he places too much tactical burden on them too early.
Surely it can't be a coincidence that most of the smaller buys (£10m and below) we've made have only come to fruition in the defensive/midfield areas- areas in which these players are taught tactical football (positional play, discipline, understanding etc) from an early age, and as such, areas in which the players have the understanding to take on board Rafa's micromanaging and tactical prowess. The less experienced players in the more attacking roles have shown promise, been brought in, but then just not lived upto their hype.
Contrast that to the less experienced Ronaldo, Henry, Messi, etc. The roles they had in their teams were freer in attack- they had more freedom to express their talent, and as such they (and others like them) turned into top footballers. I don't know if Rafa's demands of a player lends itself well to developing the attacking talent. I don't think it does, and haven't really seen anything to say otherwise.