This was written under the assumption that DM meant deadwill mine, not Dungeon Master. Our DM was overall pretty great.
Background: Player since 2014, wife and I usually do 1-2 runs each year. Gear level is HC+; We usually request HC, but if we're in a group that has the right gear and they REALLY want nightmare, we don't make a big deal of it. We're about 50/50 rares and UR tokens, we each have our class relic necklace (Rogue and Monk), kilts, and beads. No other transmuted gear of note.
The group we were in wanted nightmare, and had several loaner tokens to bring us up to speed somewhat, so we went with nightmare.
Puzzles overall felt really good. While it wasn't nearly as good as being able to experience the room, you definitely made the best of the virtual situation.
Combats: Our group took the puzzle option on group 5 so no clue on that one
Room 1: Felt okay, not a bad first combat encounter. The "save or do nothing" was a little rough, but the fact that it could be avoided if you knew the trick mitigated it somewhat.
Room 3: This felt REALLY bad. We found out afterward what the requirement was to hit, and we were not happy. The classes we play do not have access to a good option for weapons of the required "level", either due to them being out of print, or something that just wouldn't be ordinarily worth spending the transmute ingredients to get. Yes, every class can use the +3 throwing hammer, but there's pretty much zero reason a monk and rogue would spend for this item when they've got other options to put ingredients towards. We were lucky enough that two party members had weapons of the required level, so we did succeed, but half the party felt absolutely useless.
Room 7: This felt....rough. Not as bad as room 3, and we get it, last room should be a doozy. The biggest issue was time. Due to the starting monologue, even though we were able to down the necromancer, we just did not have enough time to kill the wights, so even though we killed the necromancer, we still got the taunt video at the end which....eh, again, not a huge complaint, just felt rough. Biggest complaint again would be similar to room 1, the whole "Save or be useless" thing. We actually rolled a 35 for initiative, and still didn't go first which set us up for failure in the long run.
My biggest feedback suggestion for future dungeons: Try to avoid having "nope" situations in every single combat, there were a lot of them.
By that I mean situations where a player is just told "Nope, can't do anything". We had two fights where it was effectively two dice rolls to attack: One to make the save to even act, the other to actually hit. In the room 3 fight, we more or less couldn't do anything unless we rolled a crit, by virtue of not having a shiny enough weapon token: This would be somewhat okay if we were live, doing puck sliding, because then you can have a measure of tactics and skill; people who can't hit can at least set up a backstop puck or knock someone else into the target. Being at the mercy of a virtual dice roller, the excuse of "Oh you could have hit on a 20" doesn't hold much water.
Instead of "Nope", it feels a lot better to have penalties. Something like a crazy damage resistance for the ghost in room 3 would have been better than "nope", or maybe lower the threshold of token required to something that doesn't need an out-of-print or extremely pricey weapon. Retribution damage, status effects, options that make it extremely painful to act, are all better than just being told "You can't do anything".
Something interesting just happened.