I agree, the back looks high. Check to see if
- someone added airbags inside the coils.
- someone replaced the rear springs with heavy duty versions
- someone put a spacer on top of the rear springs.
Did the PO do towing with it? They might have compensated for tongue weight by beefing up the rear suspension.
Worn out XREAS shocks won't cause static sagging, just bouncing and nosediving. Shocks won't change the ride height unless you get the kind with adjustable spring perches (e.g. Bilstein 5100, etc.)
You can put spacers on top of the XREAS shocks in front to lift it a bit. That's the only way to lift, and still keep your XREAS.