OOC:
Realistically these don't do much damage. Burning all 3 charges will do an average of 9 or 18 points of damage (depending on the save) - both Ruby and Mavis can do more than that with regular actions.
They probably work best as:
a defence for anyone with poor AC should they get mobbed;
a niche situation where Ruby (with her speed) can get into the middle of a group of minions;
a very niche situation where moving a baddy back 10' will push them into danger.