So here's my educated guess based on the real world tests and staring at a few charts. GPU-Z indicated 99-100% GPU load at all times during DR3 with framerates varying between 35-60, averaging around 45, indicating that yes, a Titan is not good enough to run that game at 60fps. By comparison, a less taxing game like DOTA2 runs at 120fps constant with 40% GPU load and Lichdom Battlemage, the AMD optimised Cryengine 3 title with everything on including TressFX, also uses 99% GPU load but is holding solid at 70fps. It's hard to look at this and say that it's not an optimisation issue. It's gobbling up more GPU resources than it really should and since it currently has no SLI/Crossfire support you can't get the thing up to 60fps stable without making some serious compromises in the graphics menu, up to and including rendering in-game assets at 720p. The only card that is likely to perform better, bearing in mind that his game can only support single-gpu cards properly at the moment is a 780ti or Titan Black, both of which are marginally faster than a stock Titan. If you're reading people saying "oh well I have a 650ti and I'm getting 60fps constantly", they're probably talking out of their arse but its worth noting that poorly optimised games often have wildly differing performance for seemingly no good reason.
Long story short, if you want stable 60fps in DR3 you're better off waiting for driver updates, sli support and patchs. You are extremely unlikely to get it right now without severely compromising the visuals.