How much they hit back or legs depends on how you perform them. You will always hit hams, glutes or lower back hard, but by accentuating the bend in you knees to could work your quads a bit harder, although I don’t think they are a good substitute for more traditional leg movements.
I guess if you work out twice a week you may have to compromise a little, and in that case, I could see the benefits of adding Deadlifts every other week as a positive move.