Perhaps an important factor here would also be the transit time of day in DXB. If it's evening (5 - 11pm) or late morning (9:30am - 1pm) the airport is virtually empty (compared to rush hour at least) and you can find some quiet bathrooms. Especially if you leave the main concourse level and go down to the security/transit/immigration levels, such as where the A-B train departs from, there are bathrooms there which are not much used and at the above-mentioned times would be virtually deserted.