The segregation of the community after DLC launches is an issue, especially over the next couple of years with the Xbone and PS4. I don't think you can have a DLC topic without bring up price. After all, money is a huge part of DLC.
Instead of offering individual sales I feel it's Activision's responsibility to sell one DLC package but discount this package. I have noticed over the last few titles that as DLC rolls out not only does match making become more random but there's also a huge decrease in overall player populations. Offering only the Season Pass but at a lower cost encourage players to stick around all year while also giving the community the most unified match making experience.
Instead of charging players for 4 DLC packs there should only be one option. You either buy the Season Pass and get all drops or you don't. Since it's an all or nothing concept dropping the price, not much, is necessary. It will encourage more players to purchase it and in doing so more player will now have all map packs.