Why Qantas hasnt looked at starting a service to LHR via the Middle East is a mystery.
This question is very easy to answer; Qantas cannot obtain daily rights from a Middle East destination to London. In-order to make the route viable, Qantas requires daily services. In the same way Qantas exited Paris; the inability to be granted daily services.
This is why Qantas has partnered up with Etihad. You will find Qantas may look at services to the Middle East down the track, however the intention is to go all the way to London and this is just not possible at this time.
These are the facts.