The 5 levels higher or lower has been proven not to be true a few times already, heck I've proven it 3 times myself, once when I got a fire priest scroll drop from a Fox Goblin outside of Sun City at lvl 84.
I think it works like this (unproven and just a theory): The higher lvl you get the less likely scrolls drop and the lower the lvl of the monster is compared to your lvl the less likely a scroll will drop.
So basically get yourself a lvl 15 and go fight some lvl 30's and you should see a few drops.