Got a nice little update..
Did some testing using the Passive + Active vs Active with success. I was able to get the F5 to successfully keep the servers in the pool during the load test using Passive + Active. When I stopped IIS on a server, it did its thing and pulled the server out, and then put it back in.. etc.
I then ran some debugging with tcpdump like you article said and discovered something alarming. The F5 would be going along good, polling every 5 seconds, and then it would just stop polling for a few minutes, and then start up again. During that time where it stopped, the servers would both be marked as down. I'm not sure what the deal is there, but I plan to open up a ticket with support to diagnose this issue. Smells like a bug to me (maybe)