Potion works for everything in Khaldun including the hidden chests. Personally I think it works better for the chests as every chest I opened had some sort of item in it. Just takes time to find chests. If doing the spawn, drops seem to be roughly the same. I usually get 15-20 per spawn and got 18 first spawn and 23 the second spawn. Potion only lasts 2 spawns depending on how fast you kill it. If I was doing spawn myself, I would only do first level and let it revert to maximize item drops.