This is exactly why I think FATEs as they are designed are poor for this game's community in a variety of ways. In truth, not only poor but encourages toxic behavior.
The reason being is the current crop of MMO players are so keen in getting to the holy "end game" that they will find the shortest path from A to B to do it. They will find any minute boost in XP/hour, any exploit (in whatever definition you want to use for it), any method if it means they can be level capped sooner. These sorts of people are bad for a game.
FATEs, as currently designed, look at this behavior and not only condone it but encourage it. They are a loud, screen covering scream that SE wants you to rush rush rush. And the wave of people rushing from one to another shows that design in action.
But what do people who do these FATE farming activities actually learn? To mindlessly spam AEs on as many mobs as possible in as huge a group as possible to get as much XP as possible in as short a time as possible.
They do not learn how to play their class. They do not learn how to actually play with other people because in truth, you don't require co-ordination for the vast majority of the FATE events if you can bring enough people to zerg it.
People wonder why you see horrible DPS in dungeons who don't handle mechanics well. People wonder why you see awful healers who would rather DPS the boss than heal the tank. People wonder why you see tanks who'll only focus on pounding one enemy instead of ensuring they have hate on everything and are mindful of the area. People wonder why you see level 50s with level 20 gear.
FATEs are why.
SE has given the lazy player an avenue to get where they want at the expense of the rest of the community. And forum Mods saying that this farming of the DD event is "working as intended" is SE saying that they're okay with players being poor. Players being caustic.
So you know what? If I see this FATE I will kill the lambs, as the FATE objectives indicate. I normally avoid FATEs, despite some of them looking like they would be fun (Svara for example I'd love to do, but not when trivialized by a bazillion people zerg rushing it) but for this one I will purposefully stop what I'm doing to make sure I complete the indicated objectives.
How can this sort of thing be stopped? How it can be made fair for everyone involved in the FATE? Enforce a manual entrance into the FATE so it can account for each type of archetype involved. So it can scale based on healers, tanks and DPS entered. So it can credit a healer for actually healing as their role is defined instead of DPSing a boss.