Knowing where you're casting your AoE and being able to manually target a location adds skill, not takes it away. It gives you more freedom and control.

I understand how some would feel about the boss AoE radius being marked, but at least it would remove doubt as to whether or not you really got out of range or not. I can't tell you how many times at Ifrit where I saw "WTF I wasn't even standing on it!"- Sometimes the graphics are very vague as to what they are affecting.

They could always make it an option such that you can turn it off if you feel it unduly takes challenge away.