Regarding the 300ms positional delay.

[Ysarel]

there's no way you should be providing visual AOE "clues" if I'm apparently meant to completely ignore them and go off either memory, blind luck or a completely different timer (cast bar) that you don't by default let my main class (WHM) see anyway.

While I 100% agree that the positional issues in this game need to be dealt with, I want to point out that you have two ways to keep an eye on the cast bar. You can set the monster as your focus target and move the focus target bar somewhere more visible than its default location and/or use mouseover macros and keep the monster as your primary target.