We have found that the channel capacity even with 100 eValid instances running in parallel is very seldom "used up."
The percentage of channel usage does vary quite a bit...but even with very heavy loads on the driver and very large pages to download...we rarely seem more than 10% of available channel bandwidth used up.
In fact, even though eValid instances do consume a lot of memory, running 100+ of them on a user account on a machine does not really tax the input/outpu capacity of the machine. When we do 1,000 BUs using a cloud-based machine image even then the I/O channel percentages stay below 5%.
So, while your point is a fair one, experience shows that the loading approach is valid up to 100 BUs per machine and beyond.
eValid Load Team