Sacred Shield is the spell all Paladins receive upon achieving Level 80.
Sacred Shield Rank 1
12% of base mana 40 yd range
Each time the target takes damage they gain a Sacred Shield, absorbing 500 damage and increasing the paladin's chance to critically hit with Flash of Light by 50% for up to 6 sec. They cannot gain this effect more than once every 6 sec. Lasts 30 sec. This spell cannot be on more than one target at any one time.
We know that Sacred Shield absorbs 500 damage + some additional amount based primarily on your spell power. In my tanking gear and casting Sacred Shield on myself, I’m able to absorb about 900 damage. A Holy Paladin is going to have more spellpower and will be able to absorb more with Sacred Shield. You can increase the amount absorbed with Divine Guardian, which I don’t have in my build at the moment in favor of Improved Hammer of Justice.
So the question is how a Paladin tank should use this tool in his toolkit to better perform his task.
As a Tank, we have two main tasks. Job #1 is to stay alive. Job#2 is to keep the Boss/Mob’s attention on us and not our favorite Mage and Elemental Shaman. Sacred Shield won’t help much with Job#2, but we can employ it for Job#1.
To determine the best way to employ Sacred Shield you need to look at your Raid Composition and your Raid Role.
First issue to address is ‘How many Sacred Shields are available to the Raid?’ You see that little caveat they added at the end? “This spell cannot be on more than one target at any one time.”
From that we know that the number of Paladins we have in the Raid equals the number of Sacred Shields available. Until 3.2 is Live, assume that all your Retribution Paladins are going to be using their Sacred Shields on themselves to minimize the kickback damage they take from Seal of Blood. Once 3.2 goes Live, Raid Leaders may want to consider assigning Retribution Paladins to use their Sacred Shields on Shadow Priests to help mitigate some of their kickback damage.
After you determine how many Sacred Shields you have available to you (that is the number of Holy and Protection Paladins in your raid), you next need to determine who each Paladin is casting their Sacred Shield on. Because a Holy Paladin’s Sacred Shield absorbs more than a Protection Paladin’s would, you want your Holy Paladins to put their Sacred Shield on the raid members who will be taking the most damage, usually your tanks. This synergies well because those Tanks are likely to be people whom the Holy Paladin is charged with Healing anyway.
If you run out of Holy Paladins before you run out of Tanks, the Protection Paladin can put his Sacred Shield on one of the Tanks that will be taking less damage, typically, but not always an offtank. If you have a Holy Paladin to cover each Tank, the Protection Paladin can put his Sacred Shield on a key non-Tank. It may not seem like much damage reduction, but it could mean one of your team survives when he might not have otherwise.
Multiple Sacred Shields do stack so when in doubt, the Protection Paladin can just cast it on himself.
You can increase both the duration and amount absorbed by Sacred Shield by specing into Divine Guardian. Currently Protection Paladins have 3 to 5 'flavor points' that you can put into roughly equivalent talent combinations. One of those options is taking Divine Sacrifice and Divine Guardian.
Because Sacred Shield is an absorb, it will work on fights like Loatheb, and can be a great help on fights like General Vezzax where mana can be tight.
You may want to forgo Sacred Shield in a 5 man. I need a little damage just to keep my mana pool up.
A good Tank knows every tool at his disposal and will use everything and anything to get the job done. Sacred Shield can be a valuable part of any Tankadins toolkit.