Plot hole: The bad guys try to enter the mall through the double doors of the entrance, but they do not use the food court entrance, which is undefended. There are plenty of them and there's no reason why they would not use it as main or additional entry point, especially considering that they put a sniper there to guard it (so it's not that they don't know about it), and it's not barricaded, just plain glass doors without even a chain.
Plot hole: Eddie estimates that the bad guys will break through Montclair in 30 minutes. Since they already broke the doors with the first car, and all that remains is a pile of rubble (with a forklift behind, even) that does not stop the passage of a person, it's hard to understand what would hold them back that long.
Plot hole: Once Ben Kingsley has decided that the assault on the mall will happen, the good guys are given an insane amount of time to talk to the kid and calm her, have a nice conversation about what is happening, hole her up in a safe position, observe the vanguard of the baddies scout the parking lot and just then do all sort of A-Team style preparations, barricading the front door and booby-trapping the entrance. The villain is in a rush, knows the layout of the mall and does not fear the unarmed mall cops; there's no way they had time to do all that. Especially since his plan consists exactly of the brute force assault ("driving through" the front doors) that a little earlier Eddie mentioned, contradicting the stated purpose of not drawing attention from passing patrols.
Plot hole: Eddie's colleagues are getting slaughtered in a shooting where they are badly outnumbered and rushed by the villains, but when he meets the group of armed feds Eddie does not even try to make them provide support or rescue his friends; he right away contacts them to have Jamie reach him, at great risk (which is what gets Mason and Vance shot). Who would ever do that? You reach law enforcement and rather than tell them to save your friends, you call your friends asking them to sortie to join you and the group of trained and armed men who are doing nothing? The whole scene is wrong on multiple levels, including Eddie's late reaction.