Hi Sonicbum,
Our SOP follows exactly what's written in the FCOM:
Go around in case of L/DEV reaches 2 dot or XTK reaches 1 RNP.
But for some guys it's whatever comes first but I don't agree with that since it's not written that way. I think like you said in case of RNP 0.3 the limiting factor should be the XTK and not the L/DEV scale. Anyway, I'm going in the sim in few days, let's see what's the instructor has to say about it.