What was wrong with the raining zombies thing?
Lots of things.
1) Zombies moan. Why didn't they hear them up on the roof in the first place?
2) Todd Bridges puts a bottle of wine back on the cabinet and the whole things collapses Wile E. Coyote style. Come on.
3) Then the zombies start raining. How come they never fell through the roof before then? They're just wandering around up there.
4) Why did the chopper suddenly fall through the roof? Because of the holes the zombies opened up? See (3) above.
I get that this is a zombie show so the writers feel like they need to come up with a way to get somebody eaten every now and then, but this was silly even by the standards of the genre.