The neck thingies have never been conclusively established as torpedo launchers.. They don't look like the tubes facing forward (or aft), and they've never been seen firing anything - only the lower hull forward launchers have ever been seen firing, in ST6, and I can't think of a time any were seen shooting in the TNG era. I believe that they have never been given a real purpose in any official source.
Personally, I prefer to think that they're simple greeblies that could be sensors, access ports (it's famously been attributed to a place where a workbee can enter the neck in Generations, though that is not conclusive), slower probe launchers, etc. If you look closely at the model, you do see that there are twin conical SOMETHINGS in each one; really, could be anything.
Mark
Personally, I prefer to think that they're simple greeblies that could be sensors, access ports (it's famously been attributed to a place where a workbee can enter the neck in Generations, though that is not conclusive), slower probe launchers, etc. If you look closely at the model, you do see that there are twin conical SOMETHINGS in each one; really, could be anything.
Mark