Divine shield, a 5 minute CD 12s immunity with a 50% damage penalty while active, it is often seen in PvP to be overpowered given its effectiveness.
The Hunter equivalent is a 1 minute CD, 5s frontal 100% parry 100% spell deflection chance.
Seeing these two actually makes me believe that Divine Shield is underpowered for its cooldown. A sensible rework for this ability would be to place it in a similar role to deterence:
Divine Shield, 1 minute CD 5s immunity, cannot attack.
This would make it an active cooldown for usage and bring it in line with the other similar immunity talent. If you are wondering why it has to remain an immunity rather than an effective immunity the answer is the protection spec which would otherwise have the most awesome tanking cooldown ever (so the boss doesn't stop hitting me and I am immune... awesome).