In regards to PVP, I used to think that no, one person did not tip the balance. However my experience grinding Warsong Gulch rep has changed my opinion because I have what could be called anecdotal evidence that suggests otherwise. I recently started grinding Warsong Gulch rep, and when I started it I found I had participated in 64 previous matches, amounting a 28-36 record (43.75% winning percentage) and earning 2590 rep for those matches. As I never cared for Warsong Gulch much because of the lack of a time limit allowing matches to grind to an hour or more, I was there under protest, and for the emblem only. Basically I counted on one match, one emblem, so I certainly never tried very hard to win.
That all changed when I decided I really wanted Justicar. From that point on I was in there, and in there to win. I've now participated in 105 Warsong Gulch matches, and raised my winning percentage to 48.5% (51-54) and earning a total of 4935 rep (2345 rep increase). In short, I was trying to win, doubled my winning matches and nearly doubled my total rep in less than half the time.
As I said, that is only anecdotal evidence. And gets murkier as we discuss other Battlegrounds. But I think certainly it makes sense. Especially in smaller groups like Warsong Gulch where it's 10 v 10. In Arathi Basin, where it's 15 v 15, I still think just one person makes a difference but in Alterac Valley, does it? I'm not so sure. It certainly could though.
I've always disliked the mobs of people that AFK in AV, and to a lesser extent those who do it in AB or WSG, but everything I've witnessed in the past couple weeks shows me that its even more important then ever to get rid of the AFK'ers. Unfortunately there are still plenty of apathetic players that just don't care. I imagine it's because they were as ignorant as I was on how much each individual counts. Case in point there was one player in WSG the other day that was afking along the eastern border behind a tree. I reported him afk but couldn't get anyone else to do it, so he got to sit there the entire match, and gain the rep and honor we all worked for. For some reason that really bothers me. Perhaps because some of the matches I've played have been close. Close enough for one person to make a difference in individual battles? Perhaps.
Naturally it gets me thinking about the new idle system that Blizzard recently implemented. It's definitely got some problems that need to be worked out, but I can't think of a better system myself. Perhaps if it added in some additional intelligence that looks at the amount of healing or damage, or objectives taken by the individual before it marks someone idle it might be more workable. Or perhaps instead of requiring players to mark it could simply do it itself using the same criteria.
All this really makes me wonder what to expect in the rated battlegrounds where people will also be earning arena points. I wonder if anyone will turn the other cheek to people afking there too?