It takes too long to ramp up with it being at 5 stacks now. It should be changed back to 3 stacks with the 6% ap scaling on the bleed and +33% impact damage per stack. Until then it still gets outshined by mutilate in almost every aspect. Maybe 40% per stack instead.
Considering that mutilate gives 2 combo points while saber only gives 1, it should make sense for saber to do more damage without needing a super long ramp-up.