Tab Targeting.

[Fornix]

To me it looks like most far away enemies not engaged in the fight have the hightest priority to be chosen as next target lol. Actually I have no clue how their system works.

This, there's no left to right involved in it from as far as I can tell. Most of the times it simply targets the most inconvenient target first, the one furthest in the back. It's like trying to plug in a USB-cable. Always takes 3 tabs before hitting the right target.

It'd be nice if the tab targeting would simply target what you're looking at most closely first, so whichever is most center on your screen.