You have the worst of any possible combination
- Booked via an on line travel agent
- SYD-DOH-DUB in F .Both flights EK operated but QF marketed
- QF 081 ticket
- aircraft changed
- half the trip done
Have you tried EK to take over the ticket?
But don't like you chances with EK or Expedia.
A map from Great Circle Mapper - Great Circle Mapper