Would a 6GB card without DP work well for workstations over Titan, if they don't need the DP, or will NV do some driver crippling as both tend to seem to do?
Titan already uses Geforce drivers, so it's not optimized for pro applications. As far as DP goes, it's not practical without ECC RAM anyway, so it's not a factor for either card in professional use.
With that said, unless you run an app that has stability issues without the Quadro drivers (not a common problem) A card like the Titan, or whatever the new card is going to be, is powerful enough even without optimized drivers to run the apps. fine. Most workstations don't have $3000+ workstation cards in them, which is what these cards are equal to, silicon wise anyway. CUDA apps should be fine as well. Unless nVidia uses some sort of lockout (like they did with Adobe Premier). Generally there are hacks to get around that though.