A tricky one, this.

I would advise against carrying the dress onboard and checking it in.

Checking it in is probably not a good idea because it could get lost and/or damaged. Carrying it onboard the aircraft is probably not a good idea either because in the hustle and bustle of boarding crew will probably be very busy and might not have time to hang your dress in the wardrobe. It also might be quite difficult to manage during the transfer at DOH.

If you are travelling in business class you might have better luck as the crew will be able to offer you more attention. But even then I would rather not.

Instead I would consider consigning the dress to DHL or FedEx. If you can, send it ahead so that it is sure to arrive in time. It might cost a bit more but will be worth it for peace of mind.