Ivica Kostelic of Croatia missed a chance to clinch the season slalom title but placed 16th, his worst slalom finish of the season.
Myhrer won the first heat and went on to turn in a combined-run time of 1 minute, 40.99 seconds, 0.49 seconds ahead of Deville.
"I heard that I really need to push hard if I want to make it and I just tried to ski as fast as I could up on top and than keep a good line in the lower section and it worked," said Myhrer, who notched his first World Cup win of the season.
Alexis Pinturault of France placed third with 1:41.57. Will Brandenburg was the top U.S. finisher in sixth place.