Whether you're staring at squares you're double clicking, or staring at the HP bars and hitting CTRL 1, you are still staring at something besides the monster directly in front of you.
Now, the other person I watched during this raid, the tank, was arguing vociferously with the team on Skype or whatever, and pretty much ignored most of his UI mods and just ran around and mashed macros.
For me, the UI not only needs to be intuitive, it needs to be completely controllable on the keyboard alone. I dislike using the mouse (even with my fancy verticle mouse, my wrist hurts after extended mouse use) and I'd rather not use it at all if I can help it. Same with the controller. When I play FFXI, it looks more like I'm playing the piano on my keyboard