One of the (many) problems the airline has is that in many of the markets it serves there is virtually no awareness of Qatar Airways among its potential passengers. In fact many do not even know where or what Qatar is. Of the carriers in the region Emirates now has very strong awareness around its route network and GF is beginning to regain its high profile .... but Qatar Airways???
As a result the only way to build loads is through discounting and I'm told for example that in the UK market QR's fares to most of the points on its network are always cheaper than any of its competitors. As long as the airline's profile remains so low it will never successfully improve its yields and reach profitability.
Not surprising that the Manchester loads are so poor. Going ahead with the launch of the route during the Iraq conflict was crass stupidity. It would have made sense to everyone to postpone it for a few months until traffic rebuilds.