OK, we're still missing a complete picture here. Is persistence configured on the F5 itself? If so that may explain the continued use of the offline node.
Is Fiddler establishing a new TCP connection when you test after marking the node offline? It's not a valid test if it's using an existing connection. This only applies if there is no persistence in play on the F5.
I can't really determine the best approach without understanding the above two points and knowing a bit more about the application itself. The reject setting is certainly valid if the application recovers/deals with this well. Happy to help.
Nimbostratus
