I had dual missile turrets on my Orca - One forward facing, and one rearward facing. With the right aspect on the target, both missile turrets would fire. Which only had an effect IF the target shields were down allready, since both missiles would allways hit at the same time. If shields were up in any way, they would just be taken down.
The only way around that, would be to chainfire the missiles, so their arrival on target would be spaced.
If you can do that, then the tactics of dual missile launchers would be sound. If you can't, then the tactics would be a waste of vessel energy.
And remember - they are called MISSiles, not HITsiles for a reason. There is no guarantee that you will hit, especially in a multi ship furball.
Out of bats, Out of bots, Out of torps - Down to harsh language...