That is a fantastic bokeh. What is the MFD on that beauty?
Have you tried "cutting it short" by using a culset? I did precisely that recently on Rokinon and here is how it looks. Nothing compared to your shots but then... No one can take away my right to be dumb right?
I was grappling with MDF on that Rokinon as well, and then I thought, why not use culset? I had plenty light, so that was not an issue.
I cut the MFD by half or so, I would guess.
I took the above one on a tripod with micro slider and a +4Culset slapped on front. Panned across taking 22 pictures, stitched them on MS ICE and tweaked a tad in HDR Machinery and LR. Not the best I could get, but it was fun. One way I compensate for my photography skills or lack thereof, just make it complicated.
I guess I am allowed rambling since I posted a flower.