EDIT: I am in no way trying to do a macroed /cancelaura Ursa Major. Removal of UM was solely to provide an extreme example.
Recently both AMR and Simulationcraft changed their stat weights from Master/Versatility to Multistrike/Mastery. With bonus armor where possible.
Is there a consensus?
I am interested in the argument for Mastery as well as HEALER's perspective, specifically since we have moved from the MoP paradigm of spikey tank damage and topping off immediately to now having room for HoTs to tick and also tank's self healing, especially Guardians and Bloods,
Here is my debate for Multisrike:
Ursa Major is percentage based.
What this means is that Multistrike is not just health but also mitigation.
Lets say at baseline you have 500K HP and you take a hit of 100K, you are now at 400K HP. That is 20% of your HP.
Lets say now that you have focused on multistrike and you have a reasonable 600K HP.
You take that same 100K hit and are now at 500K instead of 400K as before. You could take another 100K hit and be back at where you were with one 100K hit without focusing on MS. But we are talking %s so instead of a 20% HP hit that same 100K was a 16.6% hit.
This plays out even after the fact. Lets say that you have max HP of 600K and take the 100K hit and go down to 500K HP and then you lose the Ursa Major buff, or more likely it goes down from say 20% to 15%. When this happens it doesn't effect that damage already taken, it simply scales down what HP you have left based on the %.
In this example you have 600K HP and take a 100K hit and go down to 500K HP. Then you lose Ursa Major, for example all of it, and your max HP goes back down to 500K HP, but the healers have not healed you yet. Meanwhile the 100K damage taken has been scaled down because it was calculated at the 600K level and now that you have a max HP of 500K you display 416,666 HP left instead of displaying 400K HP left as you would have if you had a max HP of 500K when you took the 100K hit. The % carried over and has provided mitigation versus your baseline HP.
Now in practice it will usually not be all or nothing it will be deviations both ways but the good news is that even if you peak at say 37% then any damage taken is mitigated. Sure, in the moment of wanting to top me off healers may consider me a mana sponge, but if nothing happens, no heals come in, and I take the hit and Ursa Major is reduced afterwards then damage was mitigated and I need less healing.
For healers it is counter intuitive, especially after MoP and the whack-a-mole spiky damage we took and constant need to top off tanks.
Now we have self healing and active mitigation so overhealing room needs to be left not just for HOTS and other healers but also for tanks, especially Guardians and Blood DKs.
We will of course be toped off before specials like Inferno Slice but those are special mechanics where CDs are used, they are planned for and are not normal ability expenditure based.