Tapping Saint Traft and Rem Karolus to activate Heirloom Epic's ability of tapping creatures in lieu of mana cost for Heirloom Epic does not cause Saint Traft and Rem Karolus to create a token nor recognize that they have been tapped for the turn.
Can confirm that Saint Traft and Rem Karolus does not trigger when tapped to pay towards the activation cost of Heirloom Epic's ability. I also think this problem is stemming from Heirloom Epic and not Saint Traft and Rem Karolus because Saint Traft and Rem Karolus triggered as expected when tapped to activate Springleaf Drum in another test.