this also frustrates me. I will have myself not highlighted, and I'll still get hit, or I will have an enemy highlighted and they dont get hit. I Think its set up to highlight the spells animation and not its actual hit box.
If animation and hitbox differs ... that alone sounds like mistake.
In the words of the senior NCO instructor at cadet battalion: “If you ain’t cheating you ain’t trying. And if you got caught you didn’t try hard enough!”