Ever since I've switched to the 645Z I've stopped being so hung up on max blur. I even got the 150/2.8 to go with it, and shooting it wide open is very impressive, but going up in format did change my shooting habits to include a lot more stopped down shots. When you pay so much for extra pixels you kind of want them to be in focus.
There are two things that numbers alone can't convey, the first is that you're using different focal lengths and optical formulas for similar shots, which results in the fact that even if the DOF is technically narrow on MF, it doesn't actually look that way due to the gradual focus roll-off. Putting it another way, at 100% zoom you can clearly tell that at 150/2.8 only the subject's eye(s) are in focus, but zooming out to fit the image on the screen it looks a lot more in focus than it really is, even more so than with smaller formats. With the 85L and 135L there was a clear and sharp focus transition that you could spot in a thumbnail. The bigger the film/sensor, the more this plays into effect.
The other factor is that the 150mm 2.8 isn't exactly an "extreme" lens design as something like the fast L primes, which means that it's wide-open performance is significantly higher, except for the 200/2 of course. It still has quite a bit of fringing and isn't amazingly sharp at 2.8, but is still far superior to what the 85/135L manage, especially considering that this camera has over 2x the pixel count. Now that the 5DSR is a thing, it would be interesting to compare the performance of these lenses on a more technical basis, but honestly they weren't perfect even at 21mp. The short of it is that it's a unique combination of sharp in-focus detail and soft out of focus rendering that sets the visual quality apart.
Stopped down to f/5.6 and smaller the 150/2.8 is a friggen razor blade right to the edge of the frame, which makes it a nice dual-purpose tool, as it's softer wide open for portraits and amazingly sharp for everything else. If you can live with manual focus, the "Otus" of the system would be adapting the Zeiss 110mm f/2, which has an impossibly thin DOF while being also super sharp wide open, but good used samples go for over $2200 on eBay. You can get used Pentax lenses for super cheap, my 150mm set me back $700, and even then I think I paid too much, but it was from a friend selling his 645D so I guess I let it slide.