Tanking involves covering situationals not just constants. PvP ones are great for mean mitigation, but clicky relics give you more 'on demand' mitigation when you need it.
IE when fighting Toth and Zorn:
-113 Defense relic is useless while you are on Zorn.
- 315 Defense every other time you are on Toth is great.
Same holds true for SC/FB, Kephess, Writhing Horror and Fabricator. Depending on your strat it can also hold true for many other fights including Vorgath (thats now all of EC HM), Gharj and Annihilation Droid. I'm not sure about TFB HM yet, we're still working on it.
oh i completely agree. the on demand relics are great for zorn and toth....
but the PvP ones out weigh the push relics on every single fight other than zorn and toth.
every single fight through TFB, and every fight after zorn and toth. assuming you hvae a shadow tank and are not tank swapping on the firebrand/stormcaller fight