priority LB - maybe better suited to iRule?

Quick recap of my issue - if all nodes are down I want to serve content from another pool. We use cookie persistence - when the main nodes are available again I do not want customers persisting to the failover nodes. Initially tried this with a priority setting but persistence was burning me.

With iRule - the VIP status shows available when all nodes in its pool are down/disbaled - but no content from fail_over_pool is ever served.

domain.com-failover rule:

when LB_FAILED {
if { [LB::server pool] eq "main_pool" and [active_members main_pool] == 0} {
      pool fail_over_pool
      persist none
      LB::reselect
   }
}

This is my virtual:

virtual www.domain.com {
   destination 1.2.3.4:https
   ip protocol tcp
   profile rewrite-ssl tcp www.domain.com
   persist cookie-insert
   pool main_pool
   rule domain.com-failover
}