Am I using the targeting system wrong or what?

[Sadana]

Makes me kind of wonder how console players target their mobs though.

turn my camera so that only the name plates of the engaged targets are viewable on my screen.

Basically this.
I also take my time (doesn't take much) to make sure I am on the correct target. This is why I love it when enemies are marked. It speeds things up. I'm not sure if it's actually built into the game or just coincidence, but I've found that most of the time the target marked 1 is the first target I get when I tap the 'X' button.