Well, everybody's got their own opinions on dropping t-cases...but I think it's a bad idea for a number of reasons: (1) You giving up some central ground clearance that you gained by installing the lift so you could run larger than OEM tires; (2) Any reduction in rear driveshaft angle that you gain by lowering the t-case you compensate for by increasing the front drifeshaft angle; (2) You alter the static oiling characteristics of the engine. While engines certainly function when tilted either up or down (as when ascending or descending a hill), they are designed to have certain oiling characteristics, including gravity feeding of certain oil galleys, when the engine/vehicle is in a steady-state condition.

If I understand your post correctly, you intend to not only lower your t-case by 1.25 inches, you also intend to raise your engine mounts by 1.0 inches. That will certainly further increase the "tilt" that t-case lowering normally accomplished, thus aggravating the above problems.

I believe a far more functional and reliable solution to rear driveline vibration caused by suspension lift is to install a CV joint on the front of the rear driveshaft.