Nightmare Dungeon Strongrooms
The Escalating Nightmare Dungeon key from strongrooms is currently too rare. From my understanding, you can only get these here. In the span of 3 hours, I encountered 11 strongrooms and only found 1 key. The drop rate for these keys should be more similar to the Infernal Hordes key, where you can expect to get a key after 10 minutes of doing Helltides.
The rewards chest at the end of a strongroom seems to be binary. If your score is less than 3k, you get 1 drop. If your score is more than 3k, you get 5 drops. It seems that it should be more granularity.
Astaroth
The rewards from Astaroth are too inconsistent. One T4 kill may result in ~20 items, 5-7 of which are GA uniques or legendaries. Another T4 kill results in 4 items with 2 of them being GA items. ~20 items for killing Astaroth seems more appropriate given then time required to find a Escalating Nightmare Dungeon key and the ~13-20 minutes it takes to do the 3 nightmare dungeons. Otherwise, there will be no reason to do the Escalating Nightmares compared to other available activities.
Other Bugs: Astaroth kills you when you are looting him with a poison or something.
Nightmare Dungeon Affixes
Equipment Delves - This one has is currently bugged so I can not tell what the reward is. However, each of the artifacts that take ~3 seconds to activate, and there are about 5-7 of these artifacts to click on. If you are asking the player to click on all of these, the reward should reflect the time taken to click on the artifacts, which means the equivalent of 5-6 resplendent chests (because that is how long it takes to open the each chest). Otherwise, this affix will not be considered worth doing. Either make the artifacts instant click or make sure the reward is worth it.