This is part of why I've come to hate map packs as paid DLC: it might sound like a good idea in theory, but in practice it mainly serves to fragment the userbase. Those that only play every so often get left out from friends, and those that want to play with random strangers tend to get boned. Valve's approach is best, and it's a shame Microsoft's helped cultivate an environment where this is actively avoided by most companies, and barred from those (VALVE) that do want it to be otherwise.
Although, it might help if you got more maps with each pack! Even if it was just playing with assets for a few quick and easy maps, it'd be a lot easier to rationalize $10 for, well, 10 maps than 3.
Yup. The time before the first map pack drops in a Halo game, everything is amazing. Then the DLC starts coming out, and everyone ends up splintered.