This is normal.
Dura ace will be even 'harder' to shift than ultegra fronts because it uses less sweep. Don't sell new 10 speed shimano for people with weak hands. Or if you do, at the very least use an aftermarket cable kit like Yokozuna to drastically reduce friction in the entire system.
The spec'ed OEM 7900 cableset is 'adequate', friction wise. You will get much better performance and the least amount of shift force with aftermarket cable kits. The only 'proprietary' thing about their cable kits is,
1) Aluminum ferrules for all housing termniation except for the lonesome one on the rear derailleur loop (which is too short for about 99% of the bikes out there)
2) Derailleur cables with PTFE coating with less friction than the 7800 spec cable (big whoop, lots of people make slicker cables than the stock shimano).
The SP41 housing that is spec'ed in the kit is nothing special. It's the same stuff you can order in shop rolls.