I have searched in the archives as well as in this forum quite a few pages deep, and was unable to find a similar post. If one exists, please, direct me there, otherwise:

I had made a post on WoW forums hoping to find the answer, but the few replies I got were mere speculation. I've been reading these forums for years, but was hesitant to make a post. This would be my first.

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I am at the point now where it is time to get Heroic Arc and Heroic Shalls out of the way. (A'dal's quests). However, there are a few mobs I am wary about facing in hard mode:
O'mrogg: 2nd boss, flip-floppy aggro table. Untauntable.
Arc Sent's: in particular, the dual sent pull. Untauntable.

Things I know:
O'mrogg: He has 2 aggro tables. One for either head. Simply build threat on both.
Arc Sent's: Heavy hitting arcane bursts, really sketchy aggro behavior.

I want to know if anyone has been able to put a finger on the exact aggro behavior of these 2 mobs? I've theorized that O'mrogg's second head is the inverse aggro table of the first... I've tried distance related tactics with the Sent's... but nothing seems to work.

The most successful attempts on the Warbringer were when I tanked in DW dps gear, but with tanking weap + shield, then when the aggro flip hit, went dps crazy- gaining back aggro in a couple seconds. I had his attention for all but 10% of the entire fight.
I've absolutely no good indications on the Sent's- each time it's always crumbled down to an all-out zerg.

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I've done each zone countless times, but I am wishing to patch up the holes in the strats being used. From other heroics, I've learned that a simple plan works in normal mode, but only a solid one, with solid execution, will work in hard mode.
My gear and talents can be accessed via the WoW armory, and I use KTM and CTMod during all testing I've done, and regular gameplay.

Any insight, especially if someone actually has figured it out, would be greatly appreciated.

The double Sentinel pull got removed in the heroic so you only have to fight one of those there. I am not sure if it is intended since the taunt/growl debuff does not show, but they are actually tauntable.

I could be mistaken, but the words 'Immune' pop whenever I had tried.
I still wish to know how to best deal with them in a controlled manner, albeit if indeed there is no dual pull, I am much relieved

Trial of the Naaru: Mercy has a fairly extensive discussion on Warbringer.
The last few posts seem to be in agreement that he has one threat list and merely swaps the threat values of the person he's aggroed on and a random person.

They are immune to challenging shout but not taunt.