Is there anyway to get these besides on the maps? I haven’t encountered the maps once on live…any help
Nope. Grabbing 7 other friends who also have the map pack seems to be like the only way.
I get them occasionally, try playing with friends to increase the weighting a bit more.
If you are in a full party, you will see them, unfortunately there are only two out of all the possible maps, and both are fairly large, which makes it difficult to get them in most 8 player playlists.
I still need the 2 infection ones and the Armor Lock one. Who ever thought of the AL achievement is a huge -Yoink-. Bungie already took it out of most playlists, it was nerfed, and hardly anyone uses it. Also, assassinating anyone is difficult, particularly if the guy has a 360 degree view of the battlefield and has instant turnaround.
I also need them. :\
Perhaps we should get a Party going guys. I’ll send some Xbox Live messages out. Anyone who reads this thread after this post, feel free to message me within the next few days. 
Try looking for a gaming session for the achievements here http://www.trueachievements.com/game.aspx?gameid=2444 If there isn’t one, then make one and people will certainly join it