iRule for Single Wildcard VIP to Multiple Pools

Your iRule looks fine. You probably want to change */dev/* to just /dev/*

By default the F5 load balances per TCP connection and not per HTTP request. This means if you your first request goes to the default pool, any subsequent request down the same connection will go to the same pool. It will ignore any request to change the pool as the pool member selection is performed only once at the start of the connection.

If you need per request load balancing then apply the oneconnect profile - see article K7208 for details but essentially at the bottom of your virtual server properties you will see oneconnect. Enable the system default profile and see if that solves your problem.