[3.25] Help for Blighting - Scourge Arrow

I have played multiple leagues and still a pretty big noob. I am trying to make a Ballista Scourge that can clear Blighted maps easily. I could use a little more survivability, but I am really lacking single target damage. As it is now I am stuck between T12-T14 maps.

Any clear improvements that I could add?

POB: https://pobb.in/wA-j9QL7qM-6