While we're talking about PvP it's probably worth reminding everyone that what we're targeting is a very loose and 'for fun' system. Imagine clicking a button, being matched up against another team of equal skill and gear, and win or lose you move forward (although faster if you win) on a personal progression system that gives you some cosmetic recognition as you go. There won't be ladders or leagues, we have no intent to expose team ratings, and very likely nothing besides a win/loss record to track performance etc. etc. etc. Anyone who has tried it at BlizzCon knows the PvP in Diablo III is a blast, but I've seen some people start to get ideas that it's going to be an eSport, and that's just not something we're targeting - for the sake of our goals in the single player/co-op experience.
It's one reason custom matches can make some people nervous, because it means players can start setting up their own games in attempts to create a more competitive system. Or just complaining their 1v1 duels aren't balanced. When that happens people start demanding the sacrifice of PvE, "I need more mobility/stuns/dps", separate systems with different abilities, and on and on. I think if there were one good argument against duels and custom games, it would be the players themselves. :)
This is still a cop out man. That is like saying street fighter should not have a ranking system of any sort because some characters are imbalanced over others.
I find it rather dissapointing that you guys are using such a poor excuse to not give pvp arenas depth. Scrimages and all are fun for awhile, but won't have lasting appeal for many. Everybody already knows that it won't be balance, just like we know most fighting games are not balanced but still love the competition.