With Iafallo, it's becoming clear that he doesn't actually do anything functional in his position. The reason why he doesn't score on the power play is that he doesn't touch the puck. The scheme has him basically just taking up space in the middle of the ice to make room for the three skaters up top. Effectively the Kings are playing 4-on-4 with a pylon named Iafallo in the middle of the ice. That's not a recipe for success. You can see why the Flames were effective. They know Iafallo is not a threat to score, so they spend the entire kill trying to get in shooting lanes of the three players up top.
The Kings need to fix the power play, and it's not just personnel. There's a fundamental flaw in the way they use the man advantage. It's not an advantage if you don't use the extra man.