The shield is superfluous. If you're at 1 HP, you're mitigating all incoming damage anyways, so you're just doubling up mitigation unnecessarily. If you wanted a flat shield effect, it would need to apply when the death prevention effect ends. One way of doing this would be:

Living Dead: Most attacks cannot reduce your HP to less than 1.
Additional Effect: Grants Shield when Living Dead expires.
Shield Effect: Creates a barrier equivalent to (fatal) damage prevented while Living Dead is active, up to a maximum of X% of your maximum HP. Duration: 5 seconds

And yeah, to echo the earlier point, any 'solution' that simply changes the % healing requirement on Living Dead doesn't address the problem. The only acceptable % healing requirement is 0%.