The final reshuffle of airlines at LHR would be the main reason for the reshuffle of gates. So BA/QF flights from T4 have moved to T3 and non-alliance airlines like MH have moved from T3 to T4 (wonderful job they have done to the Gate 1 lounge).

Most airlines are keen to their flights in the same area so ease of staff to service these flights so it is a rejuggle of gates. I suspect this is more to do with the logistics for the airlines not for their pax.

Gates further away do mean that there are less hassle for planes to access the runways. Gates nearer the centre mean that pilots have to navigate the traffic of other moving planes to get to/from their gates with anxious pax wanting to get up from their seats.