Not sure if this is intentional or an oversight, but thought I'd mention it just in case-

Even though powerful pets no longer give more than a few hundred essence upon release, they can still produce thousands of essence when they grow to their final stage

Yeah, this is an oversight on my problem—pets usually produce less essence when growing to a new stage than they do when being released, so I didn't think to nerf it there also. I'm going to fix that now.

This has been fixed with today's update!