Is there a cooldown on this spell?  Seems pretty powerful when used with the discipline talent "Improved Inner Fire" Rank 3 which boosts its effect 45%.  At 60 that would be 1954.6 to Armor (1348 + ( 1348 * 0.45)).  I'm not in beta so I'm really curious how Armor affects PvP (could care less about PvE).  Obviously having to renew this buff every 3 minutes while on the run would be a pain, but if that huge of an armor boost means assist trains shred me less easily, I'll happily tolerate it.  :) 

There's no significant cooldown beyond that of normal instacast spells.

Hovering over my AC value at level 21, I have a 13.1% damage mitigation normally, and an AC of 276.  When I use inner fire, my AC goes to 606 (+330) and my damage mitigation goes up 10% (23.1%) against mobs of my own level.

For higher level content, I would expect that the % of AC due to inner fire increases significantly compared to the native AC from ones cloth armor, so in my brain, it makes even more sense to have this talent.

I think that in a raid type situation against those lvl 5000 mobs it won't matter much for mitigation, however, versus elites within a few levels, it should allow significantly less damage to get through, increasing your survivability when you can't avoid acquiring significant aggro.

im a lvl 60 priest, and i have this spell, and i have 3/3 in improved inner fire.

these numbers are what i get for my inner fire with it fully improved.  when i mouseover the icon in my buffs (that show the standard, unimproved numbers), they are less.

i think this is the fully improved version.  am i right?