RDP Load balancing (pool routing) based on user or hostname

making any decisions by username is problematic unless you can force users to supply credentials in the initial handshake, otherwise LTM has no visibility.

 

 

Maybe it's not an option for you, but you could instruct dual-screen users to use virtual A and others to use virtual B. Alternatively, if you fronted these resources with APM, you could potentially have an HTTP logon page that would do all the credential work for you and then auto-launch the rdp session to the correct resources.