Whilst it is 100% certain that the use of the peak time slots would be hugely productive to STN in pax numbers if the slots were allocated elsewhere (18 then v the average factor 180+ ) might it be the case the slots & costings to the airline are Government controlled as part of PSO obligations.
Regarding EK timings northbound that will change nicely with the start of the second daily UAE 67 from 1.7
The reason for using EK as an illustration is clear however as the DND operator is extremely happy "promoting" their airport with EK/DXB & worldwide connections thru STN so therefore if a change of airport in the South is to be considered a better connector over STN would be LHR with multitudes of the same possibilities.
My contribution was essentially STN v SEN & that Southend brings nothing extra to the table.