To the OP, the answer to this is relatively simple, IMO.
The 85L is sharper, yes. But it requires the working distance of 85mm and a much more hefty/complex lens, plus has slow focus.
The 35L is sharper, yes. But the quality of bokeh is much lower than the 50L; I'd even rank the overall bokeh quality of the 35 f/2 IS higher than the aging 35L.
The 50L is sort of a lovely bridge between these two. It has bokeh reminiscent of the 85L II, while being more workable indoors and in tight spaces like the 35L due to the 50mm focal length. Not to mention it is much smaller, lighter, faster focusing, and has less moving parts than the 85L II.
If they cloned the 85L II at 50mm at some point, that would be great. But currently, for bokeh reminiscent of the 85L II at 50mm, the 50L is the only place you can get that. It offers the flexibility of 50mm with beauty similar to the 85L II's bokeh. As no lens is perfect, the tradeoff is reduced sharpness. But for that bokeh, that is often a tradeoff worth making when 85mm simply won't work (or is not flexible enough).
As an aside, the MFD of the 50L makes for some cool effects not quite replicable on the 85L II. And, the 50L is weatherproofed with a filter!