Go to stirges in the Kerning subway, second map on the right. It has 2 large section so just go to the middle of the top and kill most of them then do the same for the bottom and keep rotating between each to keep the spawn flowing (also helps if you have another party member at bottom or top to control that sections spawn). Stirges spawn is great and they drop pots like mad, so if you loot, you won't run out of pots fast.
Also, the strige maps are relatively clean now with hardly anyone there anymore, it's great :)