The use/proc benefits of the relics are already substantial enough that they don't need additional passive attributes to make them justifiably competitive. The Power is present to make it so that you actually get some degree of additional threat generation in addition to all of the mitigation, for the same reason that tank augs have Power on them and DPS augs have Endurance. They're there to round out your effectiveness
I would have to say I disagree with this. The changes I proposed for these relics, are just the same changes they made to the on use power and damage proc relics, making them better all around then the pvp relics. These changes are just supposed to mirror that, making them not only situational on tank swap fights, but also better when used on cooldown for the greatest mean benefit.
I'm not sure why you're in opposition of bringing these relics in line with the relative value of their dps counterparts.
My changes to the shield on use relic and absorb proc though, as far as changing the proc effect, and removing absorb from the on use, I'm not really satisfied with either. I do like the idea of having more varieties of tank proc style relics.