Indie, to be honest I have no idea if there is a large Bangladeshi community here, but I would expect if they do fly to Oz they would fly to both cities, do a similar routing to the night MAS/ THAI/ GULF flights, ie: in through one city then to the other and straight out.
In regards to MEL/BNE pax figures it is good to see MEL has picked up, but a lot of that is on the standard carriers like SQ/MH/TG who have more than one flight through MEL, where as BNE only gets basically a daily service from the above carriers but also gets JL/KE/BR/PX, not the capacity of MEL but a bit more variety.
As far as SYD goes, well its probably more historical as much as anything, once QF was based here especially, SYD was going to be the primary destination, even when QF was purely an international operator, the 2 domestic carriers sat there and fed off what they brought in. Also as much as Melbourne has to offer, I truly believe Sydney is one of most beautiful cities in the world and has a stack of things for the tourist, both international and domestic to do.
One last thing, when Tulla was built it was out in the sticks so to speak, now the residential areas are creeping up on it. If it continues the loud voice of the vocal, idiotic minority who move into the area and build their houses will demand a curfew and if they make another noise, pardon the pun, will get their way
All the best.