my 750D has a great sensor, nothing to complain about, however it has 2 shortcomings:
it has no AF microadjustment, in video mode and whwn shooting moving subjects its AF perfornance is poor.
I can live with its viewfinder.
will getting 80D solve those issues, is it worth the upgrade ?
AF in video isn't satisfactory with four lenses tried so far, two are STM, the others USM
EFS 10-18 STM, EFS 18-55 STM, EF 50mm f1.4, EFs 17-55f2.8 IS USM
Then no video AF will be OK for you. No reason to think about changing the body. Video AF needs to have smooth transitions and has to behave very different than photo AF.
Video is an entirely different art, and for good video one have to keep control of the focus (meaning manual focus or more elaborate systems).
when shooting moving subjects (dancers) the autofocus starts hunting and loses the suject, I have to touch the screen on the area where I need the focus to get it back rapidly otehrwise have to wait merely a second for the suject to be in sharp focus
That is the nature of video AF, there is no camera that can do what you want it to do.
Start watching movies and see how they use focus, they don't do what you want to do because you are thinking as a photographer and not as a videographer. Subjects walk in and out of focus in movies.
BTW I have already had the 17-55 focus calibrated.
Field test this weekend.