Neither EPA
nor real world (50:50). Both the EPA city and highway cycles contain numerous accelerations and decelerations, cold starts, and A/C usage. No chance in hell:
the 2013 TDI Jetta is rated at 34mpg combined.
You might get 30mpg real world (inner-) city, and ~53 real-world highway @65mph and below, with the MT (no chance with the DSG).
That averages to 38mpg (you need to average the inverse of mpg for fuel consumption). The only reason I average ~40mpg with my Golf is that I drive a lot of suburban/country roads. And of course, the Golf TDI with its standard sport suspension is actually a lot of fun to drive.

That's not how a hybrid works. It does not "run out of battery" - it re-uses energy otherwise wasted during deceleration. But, yes, going 10,000' uphill at constant speed will not give you
the best comparative mileage - just good mileage.
That's why a Diesel is nice and good on the highway, and a hybrid is good for mixed driving with a significant (if not overwhelming) city component.
And remember: