Mechanically the OP was correct, but a part of the issue arises because of grouping monster initiative. It's a tricky balance, because rolling individually would be a nightmare for tracking in a large battle, while putting on the monsters on the same number gives them a tactical advantage. One solution to this is to use multiple types of monsters, rather than just one or two, if the number of enemies is equal to or greater than the party. This breaks up the overall monster initiatives into smaller groups.