I haven’t done detailed math but 2 things to consider:
- SS loses value anytime you have to be away from the boss because your GCD progression/lead is reseted.
- SS has a linear progression whereas Crit is exponential. At higher value, crit is better because it affect both crit rate and crit modifier

The first item is the main issue with SS because unless you’re fighting a training dummy with 100% uptime, you are going to lose some of the benefit