Aparently never. I've gotten more in normal than epic. Shouldn't this be the other way around? And one more question; is the amount of rare drops you get based on how many you already have? For example, one of my bags is full of blues and greens, and I haven't gotten a blue drop in quite a while. Whereas I used to get them with some degree of frequency. It seems like after I got quite a bit of them whatever script in the game that controls drops decided to stop giving them to me.
BTW, I am at Megara.