I think that it might be a bit unfair to let exotic WEAPONS into PVP. I mean think about it. Using the base assault rifle going up against an exotic. It's a bit unfair. However, I think that maybe they Should be included, but nerfed. That way it's fairer. A cool looking weapon, but with the same power as a classic rifle. Like halo. All weapons are standardized damage and stuff.
[spoiler]let the hate rain[/spoiler]
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That would defeat the who purpose of getting an exotic weapon. I'm guessing the difference between the base stats of an exotic and a common weapon won't be drastic to begin with.