Not using Search Query Data
Fitting that this comes right after using the broad modifier as a crutch. Search queries can give you some of the most valuable data available to improve your Adwords campaign. Many marketers think the search query report is only really good for finding negative keywords but that is only one part of it. Understanding your search terms is also a great way to find more keyword ideas to flesh out your campaign.
What you can do to fix it:
The truth is, how you search for a product, may not be how they search for it. Getting the full story will allow you to build a better keyword list, write better ads (more specific to the actual terms coming in) as well as stop those rogue keywords from coming through dragging your quality score down and Avg CPC up.