city of heroes would actually fit your criteria perfectly.....dont think of them as heroes just think of them as regular warriors in tights....in that game you can't get far without a team..seriously you can go up to like lvl 15 the most solo and thats if your a tank....everyone in the game is always looking for a party as well, and grinding in that game would be pointless since you wouldn't achieve much...quests are the major and pretty much only way to level up at decent speeds, and the game does offer pvp but its not really a big part of the game, and surprisingly the community in the game is very mature but fun at the same time so you may enjoy that