Chance to loot next items:

Tools = 10%-30%
Ores = 15%
Treasures = 10%
Ignots = 10%-20%
Soul Gems = 5%-30%
Miscellaneous = 50%

Chance to loot next items:

Tools = 5%-10%
Ores = 5%
Treasures = 3%
Ignots = 2%
Soul Gems = 1%-5%
Miscellaneous = 20%-30%

Less items.
If with each NPC kill drop rate too OP for you.