Anyone who’s used scepter knows what you’re talking about. It’d be nice if it got cleaned up, but in the meantime it’s better to grasp some pro tips.
1) Stand still while casting. No matter where your target goes (even through you), you will track them. This includes during stealth (great way to see their bearing).
2) Create space before casting. That way you can a: stand still, or b: not worry about them moving through you to break LoS while traveling. They’ll be to far away to get to you in time.
3) Cast from stealth. That way you’ll be hitting them before they can be on you to mess it up anyway.
4) Use a CC before casting. Temporal curtain works wonders, pull them into the void
In the end it all boils down to LoS. So take control of the battle and ensure LoS before firing.