the iRule will override persistence in as much as you can direct to another pool, or select a different pool member, but then the source persistence will be applied to that selection on egress. To override that you can use persist none on your selection. With regards to node priority, that only comes into play when there are failures, but there isn't a direct correlation between the precedence of persistence/iRule and a node or pool member priority. If it's available and has been promoted to service, THEN the precedence of persistence and/or the iRule conditions will apply.
Nimbostratus
