This is the worst part of Poe2, and I have no idea why they don't fix it? Your character "aims" at your cursor from the bottom of the model - the feet of your character are always perfectly facing at your cursor, however your character shoots projectiles from their shoulder and this results to projectiles being offset when shooting horizontally. All they have to do is offset where the character is facing to be from the shoulder instead of the feet and projectiles will aim correctly at your cursor