my sister-in-law left for Doha a month ago and she was on a family visit visa...and still they held her in the immigration at NAIA.They kept insisting that she was going to Doha to get a job and not to visit her family eventhough she had all the papers including the affidavit of suppport from our Father-in-law who sponsored her.
I think it will be even harder for a business visit visa holder to pass through the immigration specially if the reason to enter Qatar is not really for business purpose.