"It also occurred to me . . . that the characters customization of 4ed that I use in my campaign might feed into this self-centered play. My players characters are too specific and uniquely capable. Maybe from the start, focusing on a group goal would always be secondary to these characters?"
As I understand it, the purpose of 4e was to solve a specific problem, called 'balance.' Players bitched and moaned because the other players sitting around the table were more powerful than their fighter or druid or thief or whatever other fool thing they were running in 3.5, an imbecilic selfish childhood tantrum that the makers thought was a perfectly reasonable complaint, so they built an entire system to address it. Having now played 4e, I can see that the solution was to have every player use functionally the same mechanic in combat, but to use a lot of different words to describe it, so that the player on my right is casting a 'spell' while I am performing a 'slick threat through my butt crack move' with whatever weapon works for that. Damage? Fairly interchangeable. Character differences then became engineered to display believable, cosmetically developed marketed identities, sort of the way that 'blackberry' and 'i-phone' are TOTALLY different platforms for taking pictures, playing games, searching the internet, texting and phoning. Completely, utterly different things.
And now DMs are strangely confused when players - preached at to pander and whine about their personal status, insisting that 'me, me, me' operates as a game application, have trouble working together towards group goals. There is a point where I address this in my book, arguing the case that the DM must make the players understand that what they can accomplish as a group outweighs what they can accomplish as a rabble of self-interested persons. The weakness there is, of course, that many DMs are rabidly self-interested persons, who then have no idea how to explain to someone else that self-interest is a bad idea. How far does a fish get in teaching birds how to fly?
Admittedly, I don't cover the flaw in the book. The book seeks to give DMs the benefit of the doubt, and therefore does not assume they are all hopelessly selfish. Where I say that we should help players see the wisdom of working as a party, I have chosen to assume the reader is not a functioning sociopath who has found that running games offers unrestricted power over pathetic wannabe players. I've chosen to let the book assume the reader can tell right from wrong. A reach, I grant you. But the book has a higher standard than this blog.
Well, I can't wait to see what player complaints 5e has chosen to succor. Should be interesting.