I agree this would be a nice change to not break the shadow/sin, but more just bring it inline with everyone else. I would also suggest a change to Imbibe/Psychic Absorption to not buff the healing from Leaching Strike/Serenity Strike for healing for 6k+ every 10 seconds is a bit much for a dps class.
I think starting with these two changes the sin/shadow would be brought back to earth to be more inline with other classes. I will concede further changes may be needed, but this would be a good starting point.