I've recently seen somewhere that a 1" engine lift is recommended with a 1" body lift. Wouldn't raising the engine make your driveline angle worse? What other benifits are gained from the 1" engine lift?
Lifting your engine has the effect of lowering the rear output of the t-case and angling it downward (it pivots on the t-case mount). Especially on TJs this combination is often a perfect match for the change in rear pinion angle with a 3"-4" lift.
The front drive shaft is a CV, so the increase in angle on it doesn't usually matter.
The other reason to do it is what I have done. I raised both the engine and t-case, then had a custom t-case mount made that gave me 1" more clearance.