Feral Druid PVE DPS Lvl 60 Theorycraft

Is there anyone knowledgeable enough about classic feral to share some predictions? Mangle is extremely resource-efficient, which means you can use both savage roar and rip (and possibly ferocious bite when Furor comes online). This leaves me with a question:

Will Improved Shred be a thing? Will we ever use Shred outside of clarity procs? I did some calculations at lvl 25 and shred is slightly more energy efficient with 1 point in improved shred than mangle, but you lose out by not picking Blood Frenzy.

How much do you think the things will change at 60 and please share any formulas that you might be using? Thanks in advance, I love to theorycraft, but I’m completely at a loss here.