Simple test really and all you need is 2 tanks.

You can use full DL gear/GC gear to equalize.
Have them both use the exact same rotation for threat.
For Warriors, BB combo spam.
For Paladins, RoH spam.

Include a DPS in GC/DL gear for a comparison of threat.


Observe.


The original enmity modifer was 2x, it was changed, and my belief is that the enmity modifier is according to one's damage debuff.
i.e. Sword oath is 20% damage debuff, the enmity builder is probably 1.2
The thing is that a debuff of 20% is equivalent to a loss of 25% of your damage, so the 20% enmity modifier isn't enough to compensate, hence why Tank's in defiance/ShO create less enmity.
Even then, there is absolutely no reason for a tank to lose agro to a DPS.
The enmity generated is simply too great to overcome, and you can easily test it on a dummy or a stand still boss.

It is unwise to make statements of "Prove me wrong!', because the tools to do so are available.