What is the quality rate of intrinsic autoregulation in the heart?
My conjecture: Intrinsic regulation is done in the heart the second best, after the brain.
This idea is based on the fact that the brain controls heart's some autonomic functions.

It is an open research question how the autonomic nervous system affects the intrinsic functions of the heart - and the reverse is true too.

To answer this question, we need to understand the autonomic regulation of the heart better i.e. the inner-physiology of the heart's electrical activity.