Dimitrov is a quality player, but Raonic is a one trick pony, all he has is his serve the rest of his game is pretty average. Sure he beat Federer last year but that was Federer in awful shape and form.
Not surprised to see Raonic getting thumped, Federer is playing some great stuff and he doesn't have the weapons to hurt him when he's playing well. He got shown up by Murray last year as well, the final was a massive disappointment as Murray dispatched him with ease (just like he did at Queens a month before).