I often wonder why DME and its profit potential is ignored. Cairo is a comparable flight time (slightly more) and yet was served by the 747-100/200(1990s), then the 777-200(2001/2), then the 747-400(2003/4) and currently the 777-200. Very much more in tune with the profit the route could make - and DME is a high yield route for BA!
The other noticeable "gap" is the lack of BA flights from Moscow early morning as the current options allow evening travel only.
A 777 could easily fill its J cabins on this route.