Tank Potion Theorycrafting

Hey,

yesterday I was playing on my alt and stumbled up on this recipe: http://www.wowhead.com/item=9293

And I was wondering myself could this potion beat the earthen potion in a heavy magic scenario in terms of damage mitigated and how would that scenario look like (in numbers)?

I mean its 1/8 of the TB mirror trinket for 3 minutes sounds not too bad for me.

Good idea, but it doesn't stack with raid buff style sources of Resistance.

States this in the effect: Apply Aura: Mod Resistace - Flat - Does not Stack (126)

Source: http://www.wowhead.com/spell=11364#used-by-item

ah ok there is the grain of salt in this ^^ too bad a magic mitigation potion would be awesome.