What you were expecting to happen, and what actually happened?
Dust devil is bugged because it doesn’t hit for 5 all monsters, the last guy showed a hit of 2 instead of 5… As u can see there is still a monster left and the fight is over.
Actually the reason Sparkgrinder’s health stayed at 2 was because the spell killed him. That’s why he is still showing after the battle had ended. This bug with Dust Devil has been prevalent since he was introduced.