Hail my fellow Guardian comrades!
You really need to check out this thread > https://www.lotro.com/forums/showthr...itigation-caps
Basically on Tier 2 content mobs have the ability to ignore 6770 of your mitigation rating. We are effectively calling this Mitigation Penetration Rating. Unfortunately this penetration buff is hidden to us when looking at T2 mobs, and there is no way to see how it affects our character stat sheet.
What does this mean?
It is far more beneficial to remove some of your Morale essences in favour of Mitigation essences. For sure swap in some Physical Mitigation.. as for Tactical Mitigation, well that's situational since most incoming damage is Common.
*edit (10/07/2015 7:50 AM MST): A well-geared Guardian should not need to add extra Physical Mitigation, you just need enough to counter the 6770 mitigation penetration which is around 23,440 for Physical and I guess around the same for Tactical. The thing with tactical mitigation though, so few instances hit you with it, it's almost better to swap in tactical when needed.