Yes, it will be useful. Less thinking involved and less concern about over-reving the G80.
The G80 locker in your rear axle is an automatic-celectable locking differenctial and as such requires a slight difference in wheel speed to engage. It will, theoretically, send power from 100% to one wheel to 100% to each wheel when engaged. Very functional and actually works quite well.
The Eaton will send 100% to both wheels combined, but smoothly.
A manually selectable locker (ARB, E-Locker, etc.) will send 100% power to one wheel to 100% power to each wheel when engaged.
An automatic locker (Detroit, Lock-Rite, etc.) will send 100% power to each wheel all the time.