[toni-a]

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 ?

[Brightcolours]

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 ?

If the AF is poor in movie mode, which lens are you using? Canon's video AF is the best at the moment, with smooth transitions and little hunting, provided you use a lens capable of that. The non-pancake STM lenses are the best. The 80D has similar live view AF., so you better look at an STM lens for this purpose? Or the excellent micro USM lens.

 

You should just have the 17-55mm f2.8 IS USM calibrated instead of trying to rely on MFA, since MFA values for different distances and focal length can be very different. MFA is not a solution in most cases.

[toni-a]

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

[Brightcolours]

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).

[toni-a]

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 

[Brightcolours]

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.

[toni-a]

BTW I have already had the 17-55 focus calibrated.

Field test this weekend.