Personally, I've found it prudent to try and bounce a Stoneskin on the tank at the end of an encounter, like one enemy at around 20%, and the fight will probably end in five seconds, and everyone runs off. Out-of-battle regen should make up for the HP you didn't heal while casting SS, and they get a little leeway on the next encounter for building up some enmity before you need to heal (and, thus, start building enmity yourself.)