Posted by Kander:

So there are two percentages that are set on master drops. There is the drop percentage, which means monster X has an X% chance to drop a master spell.

Then there is the smartloot percentage, which means aside from the drop rate, if a master drops what percentage chance is it that someone will need it.

So a boss mob that has a 10% chance to drop a master and it has 33% smartloot, means that when it drops, there is a 33% chance that its a spell someone in your group needs.

If you think about it, with there being currently eventy-billion spells and abilities on a given tier, 33% that its something you need is light years better then the alternative.

I see how people see the smartloot as not so smartloot, I hope that helps.