While I agree that loss of Reckoning makes AOE grinding a little slower (basically, less seal procs to regen mana), 3 points in PoJ have proven very useful to me in pretty much every instance after the respec.
1. Heroic Sethek - when fighting the last boss, it is much quicker now to run and hide from the arcane blast behind a pillar.
2. Shadow Labs - easier to kite the third boss from his voidwalkers while walking backwards north and south. Also, much easier to run out of Murmur's explosions - I always ended up catching one or two without the speed increase.
3. Kara - the Shade fight when you have to run to avoid the explosion again.
The increased chance to avoid a spell hit is a nice bonus, but the primary benefit of the talent is better run speed for movement fights.
Given the tradeoff, I'd much rather keep the talent that makes me a better tank than the one that lets me grind slightly faster in non life-threatening situations. In any case, I only grind Devourers in Terokkar Forest for spell dmg food buff these days, and for them I just have BoW/SoW up, this regens enough mana to keep Holy Shield up and throw an occasional Consecrate now and then.
I also level my mining in caves these days, which tends to make some extra money because of chests and better mob loot. 15% speed increase also makes for quicker cave clears.
Here is my spec (48/13):
http://www.wowarmory.com/character-talents.xml?r=Garithos&n=Gothicman
The spec is mitigation and tanking oriented, but my threat is still very reliable.
