Is there any reason with the spec not to get the most of both worlds and pick up divine sacrifice while using the last 5points in seals of the pure?
You're only missing out on the 10% extra damage decrease but you still get the 30% redirect from the basic divine sacrifice, and iirc correctly you can bubble to ensure the damage doesn't push you below 20% and cancel the effect as ret, meaning the extra damage reduction isn't as useful as it would be for a prot paladin who doesn't have that luxury if he's tanking a target