Just looked at your spec and none of the retribution talents are going to help you much in aoe farming instances. Redoubt alone will save you a ton of money as you block lots of hits when you fight mobs 10+ levels below you. And if you use Sanctuary/Sporeggar shield/shield spike, those blocks equate to damage back to the mob. Its so much fun to have 30 mobs in a half circle in front of you and watching the scrolling combat text spit tons of numbers on your screen as they hit you.