There is absolutely *NO* reason for you to ever left-click on one of the animated NPCs when using the methods I listed above. Hence (since left-clicking is used for movement) it is impossible for you to accidentally move your character when you meant to issue an attack order.
Apparently, you haven't noticed that you can target different parts of an enemy. Very often, you do not want to target the dead centre of an enemy, sometimes, you want to target "higher" or "lower" parts of them to place your shot.
This is mostly an issue for rangers and wizards, not as much melee (because it doesn't matter to them how the attack is placed; or at least I can't think of a single case). But there's absolutely a difference, with a lot of enemies.
