I have generally the same observation that since upgrading to 5.0.3 (went direct from 4.9.9 to 5,0.3).
I have disabled all plugins – no change in performance.
I switch from Divi to the Twenty Nineteen theme – performance is restored to previous levels with all plugins enabled.
PHP 7.0.6 – My host is upgrading to 7.2 next week so nothing I can do in the interim.
Going to pursue with Divi folks, but wanted to share my observations too.
