All AF systems which focus at the sensor's level are usually more accurate and reilable, no matter which lens. All indirect AF systems, meaning the whole gang of DSLRs need to be adjusted by yourself, like the hands of a watch, just in a more time consuming method. And only reducing the ammount of bad focused shots. Some always will happen.
With my T6i and 17-55/2.8 I'd say 40% of shots are correctly focused. Another 40% are slightly front-focused and the last 20% are way, way front focused (e.g. infinity landscape shot and the foreground 1-2 m away is in sharpest focus). This is for simple, static scenes. I'm not talking about trying to follow action with servo mode and thin DOF.
So it's not just a matter of dialing in a bit of AFMA. I did set AFMA on my 7D but the values for close focus and infinity focus were different. The T6i doesn't have AFMA.
The focus errors are always front-focus, and never rear-focus. My error rate seems worse with the polarizer on. Bright/low light doesn't seem to matter.
I do wonder if DPAF is the panacea, or yet another gimmick? I do like bokeh but not across the whole frame...