I understand your frustrations.
But while I agree, I am still able to find fun in the game. While people complain about getting shotty snipers on valhalla way to much, I hardly ever get that map. But really, the biggest reason people get the same maps so much is because people veto certain maps almost immediantly.
Maps people constantly veto when I join a slayer game:
Snowbound
HC snowbound
Isolation
Last Resort if not snipers usually
Guardian has a decent veto rate as well.
Valhalla: if its not shotty/team snipers.
Bungie uses the Veto data to judge what the community at large wants and then prefers what the community doesn't veto.
Thus why we see so much Shotty/Team Snipers on Valhalla, so much Pit, so little Isolation, so much construct, etc... But to me it doesnt excuse the fact that the Heroic maps are hardly ever played still.
As far as the Campaign goes, if you post a thread on Bungie.net about it, usually within 10 minutes you have 3 other people willing to go through it with you.
also, i agree custom games should have a search function.
Oh Yea, COD4 rocks too. I love it and Halo