More players means more battlegrounds, yes.
More players does not necessarily mean more battlegrounds FOR YOU.
Its about the percentage of active PvPers per side, not about the population in total.
"plenty of shit going on"...
Who are you kidding? Its virtually the same everywhere. As someone state above. LFG spam and no tanks, LFG spam and no healers.
My statement for PvP also applies here. More instance runs/raids in total does not mean more instances or raids FOR YOU.
I've played on servers with 100 players and I played on servers with 2000. The problems were all the same and most of the time just in peoples heads.
If you get fed up looking for an instance group for less then an hour I guess vanilla wow isn't really the game for you.
Regardless of how you try to slice it, population matters to some people. When you're in an active guild here yes it is very enjoyable and you have no issues. I hit 60 and was bored out of my mind then I found a raiding guild that did regular dungeons and I was active and the low population didn't feel anything. After my guild practically fell apart I didn't bother returning and now am struggling to find a guild, is my fault for leaving and I accept that consequence but for newer players, the less people means less guilds for them when they did nothing wrong aside from not joining the server fast enough.
Population has a weird psychology to it, too much people and it's frustrating (see Nos), too little people and it's frustrating for anyone not a member to a guild. Though people will rather take the fighting for quest mobs over the vacant questing zones solely because they feel there will be a plethora of things to do. That's one reason why I no lifed it on my rush to 60 and for the time (I think maybe two weeks) I was leveling any time that wasn't my job, or sleeping (which itself took a hit because I was sleeping far less) was spent leveling. When I did this I quit going to the gym during that point and quit carefully preparing meals and would just microwave something regardless. Biggest reason for this being I didn't want to get to a point where I am now which is stuck in limbo and relying solely on PuGs to see a dungeon, or doing BGs at a certain time before the Alliance quit queuing. Being a player from NA this is critical as there are only two NA raiding guilds on my faction, neither of which have any need for my class/full on members. If there was a bigger NA population, that would potentially bring another NA guild, possibly more.
When you're in the ivory tower that is an active guild the server seems fine, however when you're outside of it you really feel the population. The population will affect active guilds in terms of their numbers also, that is why I've been on Nos recently is solely population despite my preference to Kronos, because I was able to find a guild. If Kronos had more players and there was another NA guild or two Horde side I would play here again in a heartbeat if I could get into one.
Population = Guilds, Guilds = What will keep players around due to the ability to raid and most guilds playing with themselves instead of pugging. Simple as that.