Seems light to me. Moose are big critters, and more weight will sure help your broadhead get to where it needs to go.
Arrow weight is only one part of the equation though. Arrow tuning and flight are crtical. If your arrow flight is not perfect penetration will be far lower. Broadhead design is also a big factor. Generally, a good cut on contact two blade will penetrate better than a multi blade.
Pentration for big animals like moose is very important, and you should pay attention to everything that can affect it - arrow weight included.