Hi, I'm Sadique. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP.
Would you like me to remote in your computer and work on this issue directly?
It will help me to understand the problem better and will give me a better insight on how to troubleshoot the issue.
Don't worry if the problem doesn't gets solved and you are not satisfied you can ask for a refund.
No problem, we will continue troubleshooting on this chat page.
Do you feel the prints are always darker than is displayed on the computer screen?
I just want to know how the prints are if compared to an image in computer screen.
Are you sure its printing this way since new?
As of first step I will suggest you to carry out color calibration.
I will give you a manual which will help you to perform it.
Please click this link to access the manual: http://support.brother.com/g/b/faqend.aspx?c=us_ot&lang=en&prod=mfc9330cdw_us_eu_as&faqid=faq00002477_010
Without wasting your time in making you do repeated steps -- please let me know what all have you tried.
I know this is frustrating but I was trying to help you in not doing those steps which you have already done.
You can still reconsider the remote option -- I won't have to ask you any question but can directly work on the issue.