yes, we know 1 damage is 1 emnity, but it is incorrect to think thats all that goes into it. I have no reason to believe that a full thrust and a random archer shot will generate different ratios of emnity to damage, however i can tell you that popping cooldowns such as blood for blood for me does generate agro. You looked at the link i gave to cite the part 1 emnity to 1 damage but then deny what he said about buffs?

"There is actually a third type enmity generation: Buffing Enmity. Every action that produces a buffing icon appears to generate Enmity. This Enmity value appears to be a flat +70 Damage Enmity in terms of equivalency. This would include actions like Regen, Stoneskin, Shield Oath, Sword Oath, Defiance, and many others. While not all actions were tested, every buffing action that was tested produced the same Enmity generation regardless of class or job. Additionally, in a manner similar to Healing Enmity, the +70 value is divided if multiple enemies are engaged. With this in mind, it is my current belief that all buffing actions produce a universal, flat +70 Damage Enmity generation.
If a monk and dragoon dont pop any buffs and dont use any threat drops, spending 100% up time on a boss, then yes the threat meter would be a remotely decent way of telling damage.