If we all look at situation oriented cool downs as Damage Reduction over time like that, then you are playing the wrong class... Go to Warrior, since they can activate IB ALL the time, and access WAY more damage reduction than a Paladin can.

No good tank activates Rampart whenever it's up, nor Sentinel, AND NEVER HALLOWED GROUND.

Those cooldowns are for either emergencies(Healer down, other is rezzing, Range issues etc), or planned spike damage.

You can NOT calculate activated cooldowns into your overall effective HP, because unless intelligently activated, you won't see any proper use of them.

Try running Levi EX, and just pop HG right away, I'm sure your group will be happy with you for that in the middle of the 2nd Spume Phase.