If I'm being honest I'd equate those numbers on a assassin build to be about the same as a dex-based sorcerer. Granted not all of the items are easy to get but you can most certainly fit in both sets and sit at 98% bypass without Grim. You definitely want to be at or above 100% at all times.
Fix the bypass problem and you'll probably have a lot more respect for Ethereal. SA set is mandatory on a top end build.