For those struggling to scrape up OC
here is a good way to farm (although there is no super fast way to do so this is the fastest Ive come across). You can accumulate about 3k OC every 10 mins where as with the "Bringing the Band Back Together" method I was only getting about 1k every 10 mins.*This video was not made by nor does it belong to me*
There has been a patch since this video has been made the enemies will stop respawning just before obtaining 500 OC, however you can turn back up the rail from the way you came to get the enemies back, you should only be traveling back to the point where you see 3 yellow sun umbrellas on the balcony of a fairly tall building (to your left if you are facing away from the bridge). You can then head back to the bridge and the enemies will be waiting for you again.
This is strictly for gaining OC there are ways to accumulate kills faster! Dont forget to equip the "Mine all Mine' weapon amp for added OC drops per enemy killed. Good Luck Grinding!