Effect of Spirit Shots on Nightshade skills?

I tried search, but all I could find were explanations of the skills that come with the Nightshade pet. Could someone please explain how useful pet SpS are when using the Nightshade's Curse of Shade, Mass Curse of Shade, and Shade Sacrifice? I didn't get any messages in the System Message Window so I figured that I would ask here.

Do they speed up cast of the skills?
Do they increase the effectiveness enough to be noticed?
What is the failure rate(ballpark it please) of the curse skills?
In AoE do I need to cast the Mass Curse of Shade multiple times to be sure it "lands"?

Thanks bunches. ^^

The shots do increase the amount of healing from Sacrifice. You can try that on yourself in town after enough btm :)

As for the Curse, I regularly play with the Shade as tank in 7x areas and it can even tank Anakazel in hero rift. So I would say it is pretty efficient!


ps: All the above are from the "casual player" perspective.

Much appreciated, especially the info on the effectiveness of Curse of Shade pet skill. Thanks.