What would be interesting is if regen sort of had a "play possum" type of effect - basically, instead of actually needing to be defeated then self-rezzing, what if, below a certain threshold, enemies would basically mistake you as being "dead", turn to leave/fight other characters, and allow you to gain your second wind/heroic resolve - basically how many comics/anime depict a character as defeated, only to suddenly come back into the fight, (never having been actually defeated).
Alternatively, lower the cooldown on dull pain, reduce it's total duration, but give it a huge absorb for a short while, to reflect you truly being (temporarily) immune to damage.