Just wanted to get some actually hard numbers on the benefit AD provides, since a lot of people are talking in absolutes - either 'AD is totally OP!' or 'AD isn't OP at all!' and very little middle ground.
Roughly 50% of the 20-100% HP hit sizes are covered by AD to the point it provides an additional hit of survivability. AD also lets hits of size 100-143% be survivable [note: Hits of this size are NOT common].
In my opinion, AD needs tweaks. It's a very interesting idea and original concept. However, the passive effect is often not needed as Healers are spam overhealing. During periods of high burst - the times when you really need the DR - other cooldowns [because that's what this ability is] are stronger. My reccomendation would be to reduce the passive effect and increase the active portion of this talent.
I think I see what you mean, if you're a tank with 45k health and you're on 25k health a hit would have to be a single strike of >25k to get the benefit of the death avoidance.
So a 45k health tank in reality needs to have a one shot of no less than about 17k and already be hovering around that mark in health, sounds to me like the real benefit will mostly be the dmg reduction not the death avoidance.
I think you are being extremely short sighted on AD, or just a bit greedy.
The new AD isn't intended to be a mitigation tool for every hit against a paladin, paladins already have incredible "passive" mitigation (if not the best). This talent would just be too powerful if they bumped it to affect more attacks. In it's current form, it's basically an extremely good "cooldown" that doesn't even require a button press, and has no actual cooldown.
This talent is useful for 2 major reasons:
1. The same way blood draining is useful, in bad RNG situations it helps healers catch up.
2. Many bosses hit with very large unavoidable strikes which at some part, at least in the hard versions of the fight, a tank must chain cooldowns in order to survive through. This new AD either delays the threshold for when you need to chain cooldowns (Think Thorim unbalancing when he's reaching high stacks). Or eliminates the need for constant cooldown chaining altogether to save your cooldowns for when you need them most (think Steelbreaker p3).
AD is NOT for the Common hit. It's for the Uncommon hit. I couldn't ask for anything more from this talent (except from what I heard bad stacking with GS). I hope blizzard only ends up slightly toning it down because it is too powerful. Not changing it because people don't see it's extreme potential.
I don't understand your greedy comment..
Looking at the spell I think you'll find it working more as a dmg reduction talent given it seems that component of it has no CD. The death bit is just an OP gimmick.
The damage reduction effect alone is OP; I know it for fact cause we (DK) had the same before it was nerfed: Will of the necropolis. And even with half the reduction (15% vs 30% for AD) it was OP.
Since WOTK the dangers for tanks is not overall damage but spike damage or big hit boss's abilities if you prefer. There is one in almost every boss, especially in Ulduar. So those "uncommon" hit, are more common than you think and, more important, they are the only hits that matter. Any tanks can survive the regulars hits with a semi-good stuff and some semi-good healers; it's this big hits/abilities than can kill you.
So a talent that reduce every dangerous hits is OP.
The "save my life part" is fine and can be considered like another CD. By the way, you say it's less powerfull than other cd, maybe versus some (but not all, I wish Unbreakable Armor was half that good), but he also have some advantage: you cant miss to push it and you cant waste it when you didnt really needed it.
Personnally, I would just keep this part of the change and put the damage reduction part back the way it was. But if they dont, they will still have to nerf it in some way (eventually like they did to wotn, by adding an internal cd to the reduction).