FFXI is a different game. Doesn't matter that enmity is more potent in that game. I played it for years too.
It doesn't take away from the fact that any difference in enmity is better than no difference in enmity.
Especially when there's basically nothing better to do with belts on WHM/BLM currently. BLM also has -enmity on it's AF. Not sure about WHM though.

Darklight is an accomplishment indeed; It being tough to obtain does not take away from the fact that the amount of enmity difference is obtainable thus possible. It cannot be dismissed, and it certainly is not laughable.

I would take a small 5% difference between my BLM and the Tank any day over nothing at all. But I will do the extra work to obtain Darklight to increase that gap so I can be a better mage as well.

That's the point.