Well, since the 2011 4x4 Hemi is EPA rated at 13 MPG City/19 MPG Highway and the 2012 at 13 MPG City/20 MPG Highway, I think that your highway mileage is pretty much what you should expect. Remember, your "four cylinder engine" is still moving a not so aerodynamic 2-1/2 ton vehicle! I've experienced similar highway mileage in my 2012 and am, quite frankly, very pleased with it, especially since I don't feel any performance compromise from the operation of the Fuel Saver Technology. Other than the ECO light on the EVIC, I don't notice it at all.
On the other hand, my city driving mileage on my local hilly roads has been as low as an abysmal 11.5 MPG.
When driving down a grade with my foot off of the accelerator and the transmission in "D" (i.e., drive), I've noticed more drivetrain resistance than I'd like. For this reason, I usually shift into "N" (i.e., neutral) when going down a grade that's steep enough to maintain my speed and long enough to make it worth the effort. Unlike the balky seven-speed transmission in my wife's 2012 Infiniti M37x AWD, the Jeep's six speed handles the shift out of and back into gear very smoothly. I typically don't engine brake, because the local hills that are steep enough to accelerate the Jeep significantly while coasting aren't long enough to make brake fade or wear a concern for me.
BTW, isn't there a TSB for a reflash of the 2011 Hemi transmission that makes it operate like the 2012 (i.e., more like a six speed than a five speed)? If so, you should probably make sure that you have the updated programming.