Redirect to pool based on incoming HTTPS URI

I've had similar problems to what you are describing in the past. The problems that I had were revolved around a default behavior in the HTTP Profile (Response Rechunking). Some traffic doesn't respond well to it.

 

 

I would suggest creating and applying a custom HTTP Profile and trying different chunking options to see if this fixes your problem.

 

 

I did check my OWA Virtual Server settings and we are using the default HTTP Profile (with the default Response Rechunking settings) so this is just a guess, but it sounds like you have everything else configured correctly.