That death scene wasn't poorly acted but poorly edited/directed.
It was absolutely poorly acted, which if we take Marion's talents into consideration, could be a symptom of poor direction. I didn't see any incongruous editing. Basic shot, reverse shot, it needed nothing more.
"If you want to save yourself the ticket price, go into the kitchen, cue up a male choir singing the music of hell, and get a kid to start banging pots and pans together. Then close your eyes and use your imagination." - Roger Ebert on Revenge of the Fallen.