From my experience having a front locker is NOT the reason you need hydro assist. The reason you need hydro assist is when the tires are wedged in a rut or against a rock.
I went from 35's and a front limited slip to 38's and a front locker and felt very little if any difference in the steering. Of course there were times when I had difficulty turning the wheel while on the trail, but it was the same whether there was a locker in the front or not.