It's actually very intuitive and reliable, just not in the way I think people expect (or in the way I expected, at least). I've played games where tab-targeting goes in order from closest to farthest, which made me very confused when that didn't seem to work as intended in FFXIV. Then I learned the FFXIV tab system goes left-to-right instead of close-to-far (and shift-tab goes right-to-left). As soon as I learned that, it's become much, much more sensible and useful to me.