Very useful and a bargain too considering what Tokina is charging for their cine zooms!
Until autofocusing in movie mode is perfected in mirrorless cameras, parfocal zooms remain the best option for video shooting. Manual focusing and zooming at the same time is virtually impossible to execute for the lone cameraman.
Unfortunately, most modern zooms today are varifocal. The sony A-mount 16-50mm f2.8 is a rare exception in recent history but it's APS-C. I'm still holding on dearly to an old Canon FD 35-105 f3.5 for interviews on my A7S. But if I pair it with a speedbooster, it becomes varifocal!