I'm on my second Rokinon, I once owned a Canon 85/1.8 and I currently own an 85L.
The Rokinon is an excellent value for a fast 85mm, but be prepared to miss focus on a lot of wide-open shots especially the closer the subject is to you. All you have to do is just breath during shutter release and you will probably miss focus. It happens, it's the nature of the beast with a thin DOF. A precision matte focus screen will help.
Sure, the Canon 85/1.8 is 2/3rds of a stop slower, but it's AF is fast and accurate.
Now you stated AF is of little concern due to the portrait work you have planned for an 85mm, live view will come in quite handy with any MF lens.
So, whatever path you choose, you'll have a winner.
True, but honestly if you're closer to your subject and your DOF is that thin you should really be stopping the lens down a little anyway.