Update:
If you actually can prove the mitigational equivilant of healing and I calculated correctly (that's the dangerous part)...assuming maximum up-time at 25 HPS....the math would be...
2000 * (1-(.3+x))*(1-(.65*.6))*(1-.4) = (512-25); where x=0.0347 or 3.47%
Then the DG Ephemeral Mending is roughly the equivilant of having a relic with 189.6 Defense rating.
Easily best relic. (Unless I jacked this up)

caveat: I know there were some general assumptions involved in the calculating of 512 post mitigated DPS, so this won't be entirely exact in real-time application.

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