Make sure "Promote Skill Target" isn't ticked.
I have rightclick held pretty much full-time, and target with Tab and Shift-tab. I've never had this issue.
Well, "Promote Skill Target" is not clicked, and I use "Target Nearest Enemy" as a quick targeting action...but I rarely target the same enemy, or even the closest.
But turning the camera is exactly how you turn your head in the game - nothing is stopping you from turning the camera by holding down the left mouse button (allows you to turn it without turning your character) and doing just that. In fact, your character will turn its head the way you turn your camera, so long as the angle isn't too ridiculous.
Also, doesn't the "Previous Enemy" keybind do just that? I haven't actually tested it, though, so I'm not 100% sure
Yeah there is something stopping me from using left-click to camera turn...it just turns the camera and not my toon. I use the right mouse button to face the enemy so I can use the left mouse button to target him. Like I said before, "Target Nearest Enemy" is unreliable and I've never been good at using Tab to cycle through targets...I usually toggle right past the one I want.
"Previous Enemy" I'll look into. :/