i just guess i can be the guy the answer was meant for 
so FWIW.
ASIO realtime metering is very deceptive to rely on, on multicore machines.
It shows how close one of the cores (the most used) is to it’s max performance.
Since overblowing one core will lead to crackles and stuff like that, it is indeed important.
But in no way it is representing the potential of a system.
To check if a system can handle more you should rely on the cpu performance, since multicore handling is standard nowadays.
If you want to maximize your available resources you should spread things out over different slots in the rack because on normal conditions they will be assigned to a different core.
To give an easy example.
Insert some extra UHE’s.
Your system will not go on to its knees.
In fact you will see that the asio realtime monitoring will get more flattened visually.
But the overall cpu will go up as is expected. 
So when using heavy resource beasts like UHE’s machinery the realtime asio monitor will deceive you visually because they tend to use a lot of a single core, but you still will have plenty of juice to use in the box.
kind regards,
R.