I'd suggest the main problem is that your Nikon D750 is a full-frame camera (an FX) whilst the Tokina 10-17 is a DX lens.
This means that as you zoom out to the lens' wider zoom settings - so towards the 10mm range - the area the lens can see isn't large enough to fill what the sensor registers. So what you are now seeing is the frame of the lens: effectively the petal shaped lens protection around the end of the lens.
Folks usually don't want the framing effect and so switch to an FX lens - say the Nikkor 16-35mm or the Sigma 15mm or Nikkor 16mm. But I believe you can also "remove" the framing petals, i.e. machine them off (pretty drastic!). I will let others comment on how you can do this. I've also seen somewhere that Tokina have a petalless version - but, again, I'll defer to others. Perhaps this is how the Jerome version was achieved? Does the Jerome lens look different to your Tokina at the business end? Have the lens petals been removed?
The Tokina 10-17 is terrific on a DX sensor camera - such as say the D700x series - but not so much on the FX cameras.