eggc
I think one of the reasons for changing the evening flight to two class is the shear number of Business people, and or high, end tourists who use that service. The ability to work most of the day and then leave late evening getting you into DBX at the start of the Business day, or with all the connections for elsewhere going East or even South makes it well used in my experience - it is the one I am always on.
With regards to freight as has been said before it does not care where it fly's from, so my guess would be that EK make more from passengers than freight, and therefore prefer to have passenger capacity currently rather than tonnage lift ability out of Manchester.
Interestingly I was recently on an EK flight to Cape Town from DXB and was talking to the crew about passenger numbers, and where the majority came from. The CSD had a quick check, and as well as myself there were a further 107 UK passengers from out side the London area she thought who had connected through DXB. What was more interesting was my return was (whisper it softly was with BA) and I asked the same question, and was told there were approximately 11 connecting to shuttles. That is quite a disparity, and hints at the "flight" of passengers from the regions to other carriers.
Regards
Mr Mac