I suspect Ford has there reasons for going with the Motorcraft DCT Fluid 2 XT-11-QDC, and I'm sure economy was one of them. On the other hand, I doubt we'll ever see any transmissions that fail sooner as a result of that decision than if Ford had used a thicker, traditional gear oil.
The focus is a relatively light vehicle powered by a relatively low-torque engine, so the DCT simply won't be subjected to the high-torque and/or heavy load conditions that would warrant a thicker, more viscous fluid. Super Duty trucks and larger for example, may require a thicker transmission fluid for various reasons, but realistically, it's overkill to use that thick a fluid in the focus. (It'd be like running straight 40 or 50w oil in the engine when 5w20 is more than adequate in almost all scenarios)
As a side note, the 5-speed manual in my 1/2-ton Silverado runs GM Synchromesh fluid which, like the Motorcraft Dual Clutch Transmission Fluid2 XT-11-QDC, is closer to water or WD-40 than it is gear oil. 247,000 miles later, it's doing just fine.
2012 Se Ingot Silver 5-Door w/ 201A & Se Sport Package
2001 Silverado 1500 RCLB 4x4 4.8L 5-Speed