WarcraftRealms.com

I want to find a realm:
That is PVE
and has the most horde players online from 4:00am until 7:00am Mountain Time (the time I am on most, not looking for a MST realm...)

is there a way to track this?

Not really a way to do a search for such info. You'd just have to browse the available data sets to find a server that meets your criteria =/