Good question. Probably not much harder than the rest of the climbing, so say 5.6, but going down over loose and exposed terrain. Finding the correct way is sort of imperative.
I would at least bring a 25M rope of some sort just in case. I remember some of the best parts of the ridge were actually finding the steeper/harder places to ascend. I have gone up the west slabs many times with no rope if that is any gauge to help.