Skywrath have an insane long range damage burst that can kill an enemy before he can react. Do not waste time playing him as a support
The main combo is W and Q as soon as you can see your enemy, keep chasing it and cast E when you get in range. he will be silenced and receiving more magic damage. Then carefull aim your ult with Rod of Atos to an easier kill. Take your time to not miss it and don't Panic
in resume W, Rod of Atos,Q,E,R,Q,Q....
If your enemy can scape initiate with E
Use the Quick Cast hotkeys, you are going to spam a lot of skill and the quick cast will make you quicker