I don’t know a top five, per se, but there are some things I see over and over.
First, lack of establishing shots by both writer and artist. You need to set a scene. Set the scene well, and the reader don’t need my detail, they supply it already. Take a panel, show the setting. It’s vital.
Second, narrative thrust. I see a LOT of writers just doing the ‘cool’ moments, the little ideas they had in their head, little confrontations and witticisms, and then there’s a fight, and then done.
That’s the same thing as an artist who draws every page as a pin-up. It’s fine, it’s not a story. You have to let the reader know WHO wants WHAT and HOW BADLY and WHY.
Otherwise you are putting racing stripes on a car with no wheels.
Third, too much pointless, meandering chatter. If the artist did a good job, a big part of the WRITER’S job is to cut down on captions and dialog where possible. We’ve all read a comic where the eye simply isn’t drawn down the page because we SEE a dog, and we read a caption that LOOK THERE IS A DOG and the characters then discuss seeing the dog, and holy crap, is that really how people think comics are made?
Show the dog.
Then you can have your characters REACT to the dog, if necessary, not just say, LOOK A GOGGIE.
Finally, I think it’s important to take a risk every story, some kind of risk. This isn’t a rule for everyone, but I think otherwise, you become the ‘safe’ writer at best, and the ‘boring writer’ at worst.
Take a risk.
Solid story advice from Gail Simone!