I agree that Raonic's game is centered around his serve, and apart from it he does not have much, even if I would use the word "mediocre" instead of "garbage". The forehand sometimes is better than that, but yeah, that's it.
Apart from the fact that some parts of his game are slowly getting better, for example the back hand, which went from complete garbage to mediocre (even if it reverts once in a while), the point is, that he has shown the ability to play his best (whatever level it is) at key moments against Federer (Doha final, but it wasn't enough) and now Nadal (where his best was enough), as some posters also noted above. This is what makes him different from most guys on the tour.
If you want an example of the complete opposite attitude, watch the first set Nadal x Berlocq tie break of their recent Buenos Aires match.