You can change Death Gleaning's magnitude as high as you want. It is the activation condition that is the problem.
Getting sustain, when the Necro does not need it anymore is missing the mark. It is during Boss fights that Necros struggle, not after!
This is Reaper's Mark all over again....🤦♂️
If anyone here says: OH! But, PVP! I swear I'll ...
Thank you for the valuable input and respectfully recommend to discuss that aspect of ESO on the PVP forum.