Persistence across multiple virtual servers.

I've never tested this, but this persistence option might work:

  match-across-virtuals         Specifies, when enabled, that all persistent connections from the same client IP address go to the same node. The default value is disabled.

So if you are using cookie persistence, say:

create ltm persistence cookie test { match-across-virtuals enabled }

Then that persistence profile would be added to each of the virtuals in question. You could do it via an iRule too, but if the above works, that would certainly be easier to support.