Apparently you missed the part about Undying Rage consuming 50% of your health *after* it ends, instead of when it activates. So all the healing you take while Undying Rage is up will be less potentially. This change isn't massive, and with Rage spec the amount of health consumed is only 25%, and really all it will do is require people to possibly throw in an additional cooldown at the end of Undying Rage, like force camouflage or medpack.