What body are you shooting on? I personally only shoot wide aperture with a 5D3 autofocus system or aperture. Yeah, the 2.8 IS Mark I sux. 2.8 IS Mark II is the only way to go. The 70-200 F4L IS is really only good for its flexibility in zoom and for landscapes in my opinion. For portraits, I prefer 2.8 and wider.
6D. I only use the center focus point, but I do think focus and recompose is part of my problem.
As a lomg time follower of the 135L thread, many sold theirs to get the 70-200 2.8 IS II. Most of them came back within a year as zoom just couldn't quite replicate the look of the 135L.
That's my concern. But I need an 85 prime no matter what, so while it is way more expensive, I think a 85L and 70-200 IS II combo is the way to go.
. 85 is a lot more versatile for full body portraits.

