You can see exactly how it affects your lootstage on your character info page:
As to it being trivial, I dunno if I'd put it that way. Certainly by the time your lootstage is "in the hundreds", you're already well into T3 loot and the effect will be pretty minor. But even there, at lootstage 200, adding the goggles will increase the odds of a T3 item (before other adjustments and calculations
*) by 40% (from 0.10 to 0.14).
T3 loot probability table:
<loot level="200" prob="0.10"/>
<loot level="201" prob="0.11"/>
<loot level="202" prob="0.12"/>
<loot level="203" prob="0.13"/>
<loot level="204" prob="0.14"/>
*If you want to see all of the calculations and RNG results, try
this mod.