not sure if i understand correctly. i may create 3 pools; one for each portal type. for the pool which has primary and secondary pool member, i would use priority group activation. so, traffic will be sent to the primary pool member unless it is down.
priority group activation
http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm_configuration_guide_10_1/ltm_pools.html
the virtual server and pool are listening on "any" port.
for health check, i might not use it but instead using LB_FAILED event to pick up another pool member if the selected pool member does not have that service running.
LB_FAILED event
http://devcentral.f5.com/wiki/iRules.LB_FAILED.ashx
Nimbostratus
