This addon will update your macros to always point at your tank, based on assigned party roles or manual selection.
Basic usage
/assist party2 #tank=party2
In this macro 'party2' will be updated to point at your current tank based on the party roles.
If you want to manually set who is the tank (if your party isn't using the party roles, or if you are in a raid with more than one tank) target the tank, then type:
/ts set