Raonic has been training in Spain on clay since he was a teenager, moving there alone for months at a time to practice with Ferrer, Almagro, Robredo and Montanes. A big reason why he had Blanco as his coach until two months ago was because of Blanco's clay experience as a player. I'm not saying this about you but when people who have only watched Raonic for the last year or two are baffled at why he seems to be a different player on clay, it's because they don't realise this is something he's been adjusting to and practicing on for a long time. He feels comfortable on the surface and feels at home in Spain so returns there every off season to work with fellow players and of course they naturally spend more time on clay so that's where he's matured and progressed the most.
When I think of him on any other surface, I see a more naturally talented Isner who at least is willing to put the work in but still hasn't figured it all out yet. As soon as someone can handle their big serves, their lack of movement and shot selection tends to be exposed but in Raonic's case he's improving so he can almost sniff that upper tier but just isn't there yet. When he first got to Spain Blanco said "he knew how to hit but didn't know how to play" and I think they've really done the work to improve that with his clay game and now after they've split, it's time for him to work on improving it on other surfaces. Just my opinion anyway