Apparently Blizzard realized that Divine Shield wasn't long enough for the cooldown, so to correct it they created a new Argent Defender. It effectively fixes a bug that causes paladins to sometimes die.
"There is an unrelated bug with Ardent Defender that makes Prot paladins more and more survivable as their health approaches zero such that it is literally impossible to kill them... though Chaos Bolt might work."
That's right: We are currently invincible, unless you can bypass absorbs.
Is Magic Duels too generous?
4 hours ago