Yeah, try messing around with your UI. For example, a basic description of my setup would be ..

Party UI -- My Target -- My Target's Target
Party UI
Party UI -- Focus Target
Party UI

This is fairly close to the bottom centre of the screen. This way I can even take my eyes off the Party UI frame for a few moments, and watch for any movement from the Target Bar (Tank took a big hit), or Focus Target Bar (enemy is beginning to cast something). If you don't like add-ons, you're going to have to track your eyes somewhere, just adjust your UI for this.

And if you refuse to change your UI for some reason, well, that's just being stubborn :P Tailor the game for you, don't assume the game's developers play the way you play and have made this game to be perfectly suited to it.