I am still convinced that the simplest way to fix this is to just houserule that demigod grants regen = your highest stat mod, rather than your stat altogether. It really is this accelerated rate of healing which keeps the seal of binding motor running (outside of this, seal just becomes a rather inefficient way of damaging your opponent, with its main use to simply disable a foe for a few rounds before the damage taken becomes unsustainable), since there is really no other way of accessing so much healing.
