I'm not sure if EU261 would apply anyway.

There is some debate, but as the EU to DXB leg was OK, and the DXB to ICN leg starts and finishes outside the EU, a delay in DXB does not come under the legislation. It is argued that this is the case even if it was all on one ticket.

I have definitely read of airlines taking this approach to deny compensation, but I have not read of any court cases to test the issue.