The easiest of all imo is to make your iss to be able to give 3 poms, it is fairly easy (and very handy tbh) with just a +8 leather set and the correct abilities.
if you achieve that you can then leave pom on autocast and set your macro:
/target fighter1
/assist
/debuffmobs
/target fighter2
/assist
/debuff mobs
if one or both your fighters are ranged DDs and they stay far enough so that the iss can't use pom because of the distance, you can add a /attack after each /target (maybe a /delay also if the are quite far) so he can move towards them and cast it
at the first 5-6 minutes yo will have a full circle reuse of your pom so after that it will be perma on,, on all 3 chars