Assuming you've checked the obvious bits like is the iRule saving correctly and there's no errors in /var/log/ltm saying it's getting TCL exceptions...
Also check for errors in the ltm log saying things like
The requested GTM rule (/Common/director-save-members-v001) already exists in partition Common.
(The important part is the 'already exists' for your iRule. If you see this the side effect is that your updates don't get loaded. An OLD version of the script will keep executing).
If all that passes, does the iRule ever get run? Do you see the counters incrementing in the iRule stats for the event?
H