Healing shouldn't really be calculated as eHP, because effective health is the amount of damage you can take before dying without healing, by definition. The classical case where eHP is used is in tankbuster design, because a heal isn't going to influence whether you survive a oneshot. Flat damage reduction, percentage damage reduction, and max HP boosts are all fair game though.

There really isn't a problem with tanks having powerful personal mitigation tools, because predicting incoming personal damage to survive is exactly what tanks do. However, invulns are a problem, because they're much too accessible and often end up simplifying/bypassing proper swap technique. I would rather they just opted for a higher tier (i.e. 60-80% DR) of mitigation tools to replace the current invulns.

I can agree that the current state of tank self-sustain is excessive, but anticipating single-target damage patterns and mitigating them to survive is definitely well within the realm of tanking.