Honestly it depends on where your gear levels are at. I calculated out my EHP from it (though unbuffed, buffed may be different) and actually heart of iron ended up being more EHP than the glyph. It really depends on your hps and your current armor.
The idea with EHP is that it is the completely unmitigated damage you would need to take to go from full to dead, effectively then the mitigators of armor could be converted into hps.
So... granted this is low values I'm just doing napkin math to prove a point.
Say you have 40khp and enough armor for 50% reduction, that means your EHP should be close to 80khp, so 40k EHP from the armor you have. Now say your armor stays the same at 50% but you increase your hps to 50khp, now the same amount of armor has 50k EHP. However if you stay at the same relative hit points but increase armor, there is an exponential curve (at I think it's 45k armor or 75% reduction) so the more armor you have, adding armor with the same amount of hit points slowly will decrease the amount of EHP you get from armor point for point, and the EHP gained from stam trinkets is more than the actual hit points because some of the damage you take will be mitigated by damage (IE if you were to take add 4k hit points it would take 8k damage to actually kill you at 50% reduction from armor)
At least... that is the only reason I can come up with as to why 1.7k armor calculates as less EHP for me than 163 stam. This is just kinda napkin math and me sort of tired late at night. I can find some people to give me buffs tomorrow night or something and buy the glyph and plug things into my calculator if you'd like and show you the numbers, but my unbuffed numbers showed Heart of Iron as more EHP than Glyph of Indominability.
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