CAD will still work really well on a gaming card. 3D design is a very big part of game development, in some cases you can design your level completely in your 3D application and it often lacks the features of a engine editor that makes things run quickly as you work. Besides that, you’re going to be working on assets that will end up being much more complex than what they’ll end up in a game.
You don’t see a performance jump until you start spending well above the cost of a GTX 1080. It’s not worth it unless you’ve got a bunch of money to spend or you’re doing something that just won’t work on a high end gaming card. That’s rarely ever the case. In a lot of cases studios will get systems with workstation cards just because Nvidia recommends it. It’s a similar case with software, Autodesk has been telling developers to switch from 3ds Max to Maya, for what reason? Is it really going to make a big difference? No, they were doing that to get studios to buy new licenses rather than keep using the perpetual licenses they already had. It’s also been the case sometimes where Quadros are actually the same exact hardware as a gaming card but with different firmware and then they jack up the price.