No Loot for You! - The Irritating Oversight in ESO High Isle's World Bosses

ESO's High Isle chapter has already been out for over a week, so players have had quite a bit of time to get stuck into it by now. 

Some adventurers have unfortunately ran into problems with the World Bosses in the new High Isle and Amenos zone which is proving to be quite bothersome. 

But what's the problem here, exactly?

Falling Afoul of ESO's Loot Limit