Reading the Patch Notes for the PTS I can say one thing with 100% certainty...

JJMaxx1980 · January 2021

Someone really, really dislikes Moonhunter Keep.

Vildebill · January 2021

If I were to guess, these changes come from their internal numbers on completion. This might be one of the most PUG unfriendly dungeons in the game.

redspecter23 · January 2021

Moonhunter keep and Frostvault may have been the 2 least completed dungeons, therefore some nerfs. Also they have been out for a while, might as well make them more accessible.

Nairinhe · January 2021

Vildebill wrote: »

If I were to guess, these changes come from their internal numbers on completion. This might be one of the most PUG unfriendly dungeons in the game.

It's the most unfriendly dungeon in general. Duo-ing all the DLC dungeons on normal, not a single other one even came close to how long it took to clear for the first time.

Varana · January 2021

Damage in that dungeon has always been overtuned to a ridiculous degree, in addition to a myriad of "normal" one-shots. Some adjustments were overdue, to be honest.