OP, have you confirmed there's any actual effect on the playing of the mouthpiece? "Compromised seal" doesn't mean anything to me; I doubt that any of my mouthpieces would actually hold the reed against the facing the way people always rabbit on about. If it plays fine, leave it alone (you did write "very small chip").
My main alto mouthpiece has a big nick right on the tip rail (not sure how I did it) and plays perfectly fine.
If it doesn't play, then yes, I'd fill the little nick. An RPC mouthpiece isn't a plastic Goldentone that you can get a replacement for $20. Make sure to get the surface dead clean before applying your epoxy filler. If you go slow and duplicate the existing/previous surface carefully, you should have no problems. We have no way of knowing, of course, whether you're an experienced woodworker, scupltor, and machinist, or a hamhanded computer driver that doesn't know a screw driver from a bus driver, or somewhere in between. I wouldn't hesitate myself to do this repair at home, but I've been doing fine tolerance work with my hands for almost 50 years.