OltonPete.
Ref:Qatar.
Much of their increasing passenger numbers are destined for Dubai, not Doha or other connections.
They fly with Qatar either for their ridiculously good value advance fares that frequently undercut Emirates by £200+ return in economy, or ever more frequently because Emirates is fully booked and they have to fly with either Qatar or Etihad. With Etihad you have a pain in the butt coach trip to get to Dubai. With Qatar, obviously you get flown there via Doha, hence why Qatar benefits more from Emirates fullness compared to Etihad.
Problem for Qatar is twofold:
The advance cheap seats they are filling to Dubai can't be making them much margin. You can fly with Qatar to Dubai for less than you can fly just to Doha!
When Emirates bring on more capacity (third daily and/or A380), the people 'forced' to fly with them disappear.
Marginal yield and fickle passengers don't make for immediate expansion looking a great idea.
Shame really as their service is first rate in my own experience.