If it helps with the investigation (I've got other things I'm focused on right now, and also struggling with... eh... let's call it motivation):
In D:OS2, where you targeted on the enemy made a very important difference, since it measured how far away things were, and line of sight, based on your exact cursor point. Especially for skills that took their damage modifier off how far away your target was - you would often get substantially more damage if you could wrangle your camera/cursor to target the furthest away pixel on your enemy, and often whether you could hit something or not was a fight-the-ui game of seeing IF there was a pixel on the enemy that it would give you a clear line for.
If they have lifted the majority of their code base from that (they have), then it's very likely that it's measuring distance based on your exact cursor position on the model, so in the case where you and your target are close to the right distance/elevation apart, it will change based on where you aim.
Aaah eurojank
