I am still on AE15.1.2 so I don't know if this is fixed already, but:
I made use of the Master Properties in my latest Project.
It was 3 different subcomps where I used each about 10 times with different text and some other properties.
My 12 sec animation took around 4hrs to render.
Now I switched back, deleted all Essential Graphics stuff aka Master Properties and made 3x10 Subcomps instead.
The 12 sec animation then took about 3 mins to render.
Something has to be done about the MPs!
Paul Uusitalo (AE Quality Engineering) commented
Could you send me a copy of the Project with the Master Properties enabled?