I personally think blitz % is the way of the past, but a safe way to keep yourself in check with newbies at AI and coordinating.
I used to have it from 10-30% regularly last season and I was very successful.
Optimum blitzing requires gameplanning. Got a Marty Shottenhimer (however you spell it) that runs the damned ball up the gut 3rd and 15 among a ton fo other situations? Set up run blitzes that put multiple LBs onto the LoS to stop yardage.