A question about AoE DoTs

[Hezzlocks]

I don't know why pouring salt on the earth would hurt most enemies in the game, much less our party members.

Easy. By salting the earth, you are preventing crops from being grown there, thus limiting the world's food supply and causing a worldwide food shortage. The more you do it, the worse it will be, causing mass starvation and millions of deaths.

Enemies know this to be true, and thus are dealt damage from the sadness and regret of the bleak future to come.

The WoL is just an ignorant bastard with no thought towards the future unless someone tells them to think about it. Thus, we do not take damage from it. But be warned, because one day a big bad will whisper the fact into our ears, and we will be one shot by the sudden realization that we have salted all the lands of several great nations already