See this I don't understand haha. Some people say they play DLC maps in MM all the time, and other (like me) almost never play them. I have never, to this day, played any DLC map in BTB, even when searching with parties of 5,6+. Just looking up some stats right now for myself. Team Slayer is the most popular playlist in the game, and only 8 players. I have never played Anchor 9 in the playlist and I have played Tempest 3 times. (Also for the record, the other DLC map that is there is Condemned, and I haven't played that, although it just came out, so I'll let that one slide.)
As for the requiring DLC in H3, I don't agree with that. Although I wouldn't be crying bloody murder if they did it in Reach because I would love to play the maps that I have paid for, I don't agree with the principal. You shouldn't require players that paid 60 dollars for a game to pay more just to keep playing it. Maybe some minority/specialty playlists would be okay I guess (MLG and say something like Action Sack from H3 that uses a bunch on Sandbox stuff), but at one point in H3, Ranked Team Slayer for DLC required with paid DLC out there. 4v4 Slayer IS Halo to a lot of people, and to lock people out of that playlist is completely unfair.