With a normal stake (2,25 Mil XEM) I've been harvesting since the beginning mostly during the day and I've harvested 462 XEMs from 8 blocks and 4 of them had 0 xems (emtpy blocks with no transactions nor fees). It is a lottery, you may find a block which will hold a 1000 xems in fees and also you may find a block with 0 (way more often).
I got a 1200 harvest and the others just plain 0, so you are right
I have way less than 2M btw
Found a block with 6, 4, 364, 1200. Im happy but I've found a few 0's as well.