Most seem to think it´s overpowered. Splug calculated that our EH raises by 10,5% or so, if it´s only damage below 35% that gets reduced, raising it to the Blood DK levels with Blood going down a fair bit. If it´s not, its overpowered as hell and someone bribed the chiefdeveloper or hit him with a bat.
Also WotN in his unnerfed version is cited as the overpowered example of this ability. IIRC the complete hit was reduced, not only the part below 35%. I was 15% reduction and considered to be too imba.
I would say, it would put us on parity. The Blood Dk got quite a lot of Eh from armor, life and better avoidance. He also had two cooldowns for all kinds of damage and one against magic on low duration cds.
We still have one and now Ardent Defender. Cheat Death once is nice, very nice but if the situation is hairy, it will get you out of trouble once. Last Stand or Survival Instincts give you health for a longer time, when you need it. Ardent Defender is not Last Stand probably, as it also provides a needed EH increase. It seems to me that Blizz thinks that the lack of a second cooldown with a longer duration and he need for more EH justifies the overpowered looking nature of Ardent Defender in its new shape with cheat death thrown in.
I agree with Splug that the nerf bat for the dk class is big. Losing IBF, armor, health all in one go seems like Blizz is overnerfing a fair bit.