Taufiq: First of all I write the full name of the person posting at QL. I don't turn Mohammad to "Mo" and "Jesus" to "Jes" and "Catherine" to "Cat" and Ahmad to "Ah". A few seconds of extra effort to write a person's full name gives the person respect and importance. And then shortening the name of prophets!
Now coming to your query, the fact that you do not yet have a marriage certificate is a bit unusual and yes you will be facing problems not just at the airport but also in Doha.This is simply because there would be no way by which you could get to prove she is your legal wife. You will face difficulties no matter through which visa you try to get her here. Even for getting here on a tourist visa, I am sure you will be asked for a marriage visa.
Suggest you get a legal marriage certificate first before you attempt to bring your wife to Qatar.