I am a citizen, and my wife was denied twice for a tourist visa (not here in Qatar). If you can show that you can support yourself, have a good reason to want to visit, and show that you have ties, obligations, and good reasons why you will return form your visit. They will issue a visa, but it will be upto the officer at the window. I do not think the NOC is even one of the requirements, that is a Qatar thing. Here is the link...

http://qatar.usembassy.gov/niv.html