Here is my take on this subject. I TOTALLY agree that noone needs 600 grain arrows to hunt whitetails, but at the same time, I have no problem improving penetration by shooting a heavy arrow.
I think todays bows are more efficient and are perfectly capable of shooting heavier arrows for increased penetration while still maintaining acceptable cast.
I wouldn't go so far as suggesting 600 grains for a 45# bow is a must, but I wouldn't be afraid to shoot a whitetail with one either.
Use what you want .... something that shoots well out of your bow. Like a buddy of mine always says, keep it simple Fred, it's only two sticks and a string!
Having said that, I would try and keep it at 10 gpi or above. Not all shots are perfect and one day you may need the extra punch.