The Showdown Effect can be quite fun - at least with playing with locals the ping will be fine.
The Incredible Adventures of Van Helsing - Great game lots of co-op and even some PVP if you are in the mood for it.
Alien Swarm - Good fun with some friends, isometric sci-fi shooter. Also FREE.
Bulletstorm is not exactly indie but the co-op/mp is fun for a cheap price.
"What's with the poop face?"
http://www.pixelprospector.com/44-fr...layer-edition/
The above link may have the answers to your questions.
Hope it helps
and here is the reason why I am looking for indie games with multiplayer