how important is it to pull a seperate neutral for each circut in a 277v comercial lighting application

 

Speaking as a person who has not seen a drawing of the project and has no idea how proficient you are, When the neutral carries the load current for the fixture, every fixture needs a neutral the same size as the hot wire, and the neutral wire has to go all the way back to the breaker box, and each fixture also needs a "bond" wire, all the way back to the breaker box.

Speaking from an electron's point of view, you could pull one, extra fat neutral and connect that to a bunch of loads, but I don't think it's legal. Sometimes the code errs on the side of safety, but most people like it that way. Keep it legal and you won't be explaining how the fire started.