Regardless of which aircraft will operate the route, it is all about the actual number of bums on seats that CWL can attract.
In 2016 QR carried the following number of passengers to DOH from the UK regions:
MAN-DOH: 336,461 (293,357 in 2015)
EDI-DOH: 133,983 (115,529 in 2015)
BHX-DOH: 110,585 (208 in 2015)
Looking at the above numbers, BHX and EDI, which handle over 10,000,000 passengers per year have still only been getting under 150,000 passengers per year on their DOH route. These routes now operate daily on a B787, so where should CWL really be setting their expectations given they now handle in the region of 1,350,000 a year?