Considering the 'Range-Everywhere' burst of the Sunburst power of the Morrowfall, I was thinking that perhaps the artifact could be more open to something more defensive/protective instead of Death Star-ing undead and being middling other times. Perhaps we could get a list of abilities so DMs can custom design it.
Subnburst could become Aura of Life. 1/day the Morrowfall can radiate a 30' field, all non-undead inside the field can make a saving throw whenever they are inflicted by level/energy /ability drain. If successful, they lose only half as much.(Minimum 1).
So while this isn't perfect Death Ward protection, it can help take the edge off.