"I picked up a Canon 7D used recently and I'm having some really big problems with the autofocus."
I know you ae not going to like hearing this but almost all focus issues are from the user and not the camera or lens. As high as 90% and micro adjustment is one of the biggest causes because it is so misunderstood. Second is Ai-servo mode so I never recommend using it unless you find One shot isn't getting the job done. One shot will get 90% of all shots. Now this is not to say there isn't a problem with you gear as it very well could be.
The solution is to test it but under very strict conditions. A tripod a static subject or target. Controlled settings and conditions. Not willing to do this or go this far forget trying to determine whether its you or the gear.
"I've done a hard reset, cleared all the settings, cleaned the sensors, and done micro AF adjustments ..."
Good to reset and that is first thing to do. Cleaning the sensors is not only bad but a very bad thing and could very well be or cause the problem. Of course al AF adjustments need to be set back to zero. However set up your testing range using Av mode at first after the full reset. Set up a target 25 or 30 feet away. Center focus point. Good light for good exposure and good contrast in the subject especially with vertical lines. Perhaps a book or newspaper. Everything is rock solid. You are going to go through several aperture settings. You never change more than one thing at a time. You change the aperture OK. You change the distance, OK. You never change the aperture and distance at the same time. as an example. Its tedious and methodical but this is how you test a lens.
EB
EOS 1DX and 1D Mk IV and less lenses then before!
