Eternal Defender should heal me whenever I go below zero HP and do not die. I wear a nice pair of LGS boots that have my death point at 128+64+32+40+10 = 274.
I have several times been struck below zero and not received a heal. And the first thing I looked at was my turn undead, I had plenty of charges left.
Its really frustrating seeing yourself go to -84 not get healed and then die.