OK, so I finally got around to replace the brake hose, and nothing's changed. After a 20 minute drive the front brakes are hot, the rear right one is impossible to touch, and the rear left one is barely warm.
Per owlman's post, it's most likely the caliper, but it was replaced like 4-5 months ago. Could it be defective from the get-go?
Or maybe it's the left rear that's causing the problem? On the other hand, the rear brakes are supposed to be colder than the front ones anyway.
Could the wheel be out of alignment? About 3 years ago, I think I had to replace the wheel bearings on the right rear wheel. Is it possible that it somehow started this problem?