I was looking at why an item would not drop for me (which is likely just random chance) but I noticed:
loot.xml
<lootgroup name="groupModAllScaled">
<item group="groupModAllT1" prob=".2"/>
<item group="groupModAllT1" loot_prob_template="QLTemplateT1"/>
<item group="groupModAllT2" prob=".2"/>
<item group="groupModAllT2" loot_prob_template="QLTemplateT2"/>
<item group="groupModAllT3" prob=".2"/>
<item group="groupModAllT3" loot_prob_template="QLTemplateT3"/>
</lootgroup>
This is an example of about 20 occurrences where an entry tries to reference a loot_prob_template ... but instead points to a quality template which does not return a probability value at all but returns a quality value of 1-6.