It's not even the free heals, it's the fact that bosses hit tanks like wet noodles. Sometimes I forget Kardia in Savage, realize halfway through the fight when the tank is dipping a bit low, switch it on and pop Soteria and still don't need to go near any single target heals.
Kardia itself is extremely strong. It can easily reach up to about half a million tank healing on either part 1 or 2 of P4S for me. That's about 37 Druochole or just over 11 minutes worth of Addersgall generation. The reason it's not relevant is tanks just don't take real damage. I barely even need Haima this tier. Boss autos tickle.
