While wide open, the lenses are not super sharp, you generally do not want portraits to be super sharp anyway. If the images are really oof, try using live view and live AF. If the results are better, you need AFMA. AFMA is difficult to do properly, I messed my AF up when I first did it. FoCal gives excellent results.
There are some zooms that are sharper, but they don't open to f/1.8 either.
I am using Focal for calibration and it has improved the lens sharpness without AFMA but it's still not enough.
And i don't shoot anything below F4 so i'm not bothered about zooms not going to f1.8..because the 24-70 goes to f2.8, and with IS..it's as good as 1.8
Certainly, the 24-70mm L MK II sounds spectacular, and I'm tempted. I would expect it to be better, looking at the price.
I mostly use my 135mm L for portraits when space permits. The 85mm f/1.8 is no slouch. I'm not entirely enthralled with my 50mm f/1.4, but I mostly use it at f/1.4. It is a good lens.
My 2nd 5D MK III arrives Monday, and I may very well try the new 24-70mm mk II with it.
The issue is that in low light, I need the wider apertures, and I already know that the 5D MK III only adds 1/2 stop in RAW so it does not make a f/1.4 out of a f/2.8. Even if it added two stops to my 5D MK II, I'd still want to lower ISO and shoot with a fast prime.
I went for the hype earlier and bought a D800 with the nikon 24-70mmg. Nice camera, but not at IS0 12800 which I found myself using with that f/2.8 lens. The Nikon 24-70 had horrible CA when at f/2.8, so the combination was wonderful under ISO 800, but not worth the trouble at 12800 where it took a minute or two for NR to run.