Are my mitigation numbers off ?

[Reynhart]

You would have to do something goofy where DRK's damage done was based off the DRK's stats, but the leech was based off the incoming damage. If you do what you're suggesting, then DRK damage would scale based off the boss's outgoing damage instead of his own gear.

Wrong, the DRK would have to gear for survival. To reflect the damage, you have to survive it first, so you would cling to any HP upgrade you can.

And again, the problem with WAR was not the scaling, but the bad synergy between Wrath and Inner Beast. It was stupid to sacrifice your healing boost for self-healing, of your self-healing for healing boost. If WAR could have used both at the same time, I'm sure it wouldn't have any problem clearing all content.