I admit, I don't have concrete evidence of my "majority" claim, but of the thousands of players I have played with until today, all of them play exclusively for PvP on D2. That is more than enough evidence for me to make my argument.
So, take your own words of advice and "Don't presume that your opinion represents the majority." Because as far as I can see, your argument is taken from your experience also.
This is just a guess, but I think that the people at Blizzard have a better idea of what the majority wants, as well as more concrete numbers than the vague "thousands of players" you've played with. If the D3 team is saying "Hey, PvP is not our main focus, it's not why people play Diablo," I think it's a safe bet to say that hardcore PvPers are in the minority.