Upgraded to Mac 12-core, have same ASIO/CPU in Cubase

I am getting fed up with hopeless performance on my 12 core Mac. My latest project has 7 instances of GrooveAgent LE (my go to sampler), a couple of massive and a couple of Omnisphere and 8 audio tracks so pretty damn small really. I have used some processing, a few instances of EchoBoy, Decimort, Decapitator, a couple of aux send reverbs, Hammer DSP and The Glue on the mix bus. I keep getting overloads, stutters and crackles.

I took a screenshot of my activity monitor and Cubase and while Cubase is maxing out my Mac shows 85% idle. I have tried different buffer sizes, multi processor and AISO Guard on and off etc. and very little significant difference.

Just what is going wrong with my system?