This was supposed to be defensive tank mythic that puts extra pressure on your stamina in exchange for mitigation. I like the concept, but as it is now, it's targeting what is not problem in the slightest. Tanks already have enough options for dealing with direct damage. We have Bracing Anchor, Immovable, passive block mitigation and such. There isn't a single fight in which you die due to insane direct damage. Even more direct damage based fights such as Archdruid Devyric have been done on 3 dd setups by stacking block mitigation. We don't need more of it. Also for people that don't know how to sustain their stamina, current itteration of this mythic might effectively turn into noob trap where they drain themselves off their stam in fights where you would not even utilize block at all, such as harmless trash pulls. This helps no one.

The biggest problem at the moment for tanks is dot mitigation and this should be the niche this mythic might be able to solve. So change it to something like 50% dot mitigation and negative 800 (or whatever number might be fit) stamina drain like Spaulder of Ruin does. You would still have to mitigate direct damage with block, but some of more punishing dot fights like Bahsei, Taleria or even 4 man stuff like Arkasis might be more manageable for your average tank.

It would also become much less disruptive in PvP because majority of the damage there is direct damage, sans few pressure builds using master's weapons and procs in general. It would be much healthier mythic for both PvE and PvP.