From what I have heard from other players and experienced myself of Pro mode, it seems arbitrarily and artificially difficult like you mentioned.
Some of the included "difficulty" options make you think "really?" and often make no sense.
Then there's the whole challenges aspect where it seems IO haven't really put much thought into it, and just used the normal difficultly challenges on the professional difficulty which leaves you thinking, do I really want to do the same thing again just for some unlocks?
IMO I think the Professional difficulty idea was good in theory, it's just executed poorly. I'm looking forward to some work being put into it, because in it's current state I find it hard to justify replaying everything again.