A top-spec Mac Mini is pretty beastly at $1500. I have no doubt it would chew up and spit out the vast majority of workstation use cases. 2.6 GHz Quad-core i7, 16 GB RAM, SSD.
The only thing I can possibly imagine would be some seriously high-end 3D rendering or massively parallel simulation software.
To the OPs point, there is zero reason to get the Mac Pro over even a Mac Mini.
Seems like there's a hole in Apple's lineup. You can't get a discrete GPU without a monitor attached (iMac) or spending >$3000. Not that it matters much for Illustrator, Photoshop, etc. which are not GPU-parallelizable anyway. At least not yet.
The only thing I can possibly imagine would be some seriously high-end 3D rendering or massively parallel simulation software.
To the OPs point, there is zero reason to get the Mac Pro over even a Mac Mini.
Seems like there's a hole in Apple's lineup. You can't get a discrete GPU without a monitor attached (iMac) or spending >$3000. Not that it matters much for Illustrator, Photoshop, etc. which are not GPU-parallelizable anyway. At least not yet.