I keep a very close eye on my 6 (soon to be 7) SolarWinds boxes. Without Solarwinds we are blind.
So something I think I have noticed is that even if you have other pollers adding more load to them still increases load on the main box.
I have been adding a lot of nodes and interfaces to my 2 additional pollers giving them increased workload which is visible but I have also noticed greater load on the main box.
Is this just coincidence or does the main box get busier by some fraction as the other pollers become more active?