With the No Stranger To Pain talent, the tooltip says it absorbs 50% of damage up to a total of 1.9M prevented.
Except when I use it, I get a shield that absorbs between 300-600k. Nowhere near 1.9m.
My expectation would be that if I took 4M damage after pressing it, I would actually take 2.1M damage. But I take 3.5-3.7M.
Is it just broken or am I missing something?
Ignore pain or as I like to call it, Ignore Brain allows it to stack up to 3x from memory.
Assuming you hit it on cooldown 3x every 11s on the correct tick without taking damage you would stack it to full if I remember correctly.
Ignore pain’s tooltip on what it does is a bit wordy but to put it bluntly, it makes you take 50% damage until the damage cap it’s ignoring is hit.
EG: 100k ignore pain shield, take 100K hit, 50k is ignored, 50k is taken off your health bar.
Overall it’s a solid defensive use of rage when you’re disengaging from a target in PvE or about to take spike damage. It’s a mainstay in PvP though for survivability.
Ignore Pain is on an 11 second cooldown and only lasts 11 seconds. It’s not possible to “stack” as far as I can tell?
It is possible, please read the second sentence again.
Assuming I hit the cooldown of 11 seconds every 11 seconds I can 3x an 11 second buff?
That makes no sense 
You can stack the buff, and much like ignore pain it doesn’t make sense
They changed the tooltip back in dragonflight to reflect the maximum amount ignore pain can reach, which is 30% of max health, rather than the shield each press will give you. Was such a stupid decision.
Anyways, Ignore pain has an attack power coefficient of 4.375. This attack power is not your base attack power which is 1:1 of your strength, but rather a formula that takes your weapon damage into account
attack power = weapon dps * 6 + strength
This attack power is then multiplied by its coefficient of 4.375 and then amplified by any attack power bonuses you have (battle shout, protection warrior mastery, etc), versatility, and the hero talent to get you your actual value of ignore pain. Protection warriors additionally have a 2x multiplier on ignore pain.
So take me as a prot warrior for example.
I’m using this sword and have 5.31% vers, 17.2% attack power from mastery, and 39,410 strength.
so we have 898.1*6+39410=a base attack power of 44,798.6
so 44798.6 * ap coefficient * battle shout * prot mastery * versatility * hero talent * protections 2x multiplier
so 44,798.6*4.375*1.05*1.172*1.0531*1.15*2=~584,194.
Which brings us to close enough. Missing some decimal precision on versatility and mastery.
Perfect, appreciate the detailed response. Thank you.
I honestly barely even notice it given that most classes hit for this or more in a single hit. Being a 4-6% shield every 11 seconds isn’t great 
(For PVP). Seems pretty weak for TWO talent points but maybe I’m just not using it right.
I tried using the alternate talent (Storm Wall) which heals you 5% on parry but as far as I could tell, it’s broken? I didn’t record a single proc during an entire battleground. Maybe my damage meter just didn’t track it, not sure.
You won’t rng parry anything in pvp, so the only time storm wall can get value is during die by the sword