When you are trying to destroy the comet, after you break it up into fragments or shards and then when you break those up two D7 battlecruisers come after you. Take care of those and then proceed to work on the comet again. It significantly reduces the difficulty of the mission. I learned this through trial and error.
The other thing is on What Lies Beneath, the flashlight needs to be fixed so it actually works.
The fact that the flashlight fails often is in the flavour text. I think it is deliberate so that you get the haunted house/horror movie effect of the lights going out or not being reliable.
My biggest problem with the Devidian arc is that it's placed almost immediately in front of the "Past Imperfect". So we have two TOS-themed time travel missions almost back-to-back. Not really sure what they can do about that, though.
The current bugs with What lies beneath is known to the Devs, this was introduced with season 8.5. Hopefully it will be fixed as soon as.
As for Everything Old. Are you meaning the point in the mission where you have the NPC walking back and fore. If so, then what you need to do is when he has started on his walk back run around the outskirt of the room to the right, careful not to hook up on the crates at the far end, then once done, you will be able to use a diplomatic response to the group of NPC's in the next room.
No it's the last group after that. I never get a diplomatic response, the button says "speak to the security team, but clicking it only gets me the "attack" option, there's no dialogue at all.
I could understand if it only happens to KDF factions as they're likely to just stun everyone in their way, but this also happens to my fed characters trying to sneak past everyone.
The only real grip I have with the Dividians is that they aren't presented as a threat in the same way as they were in Time's Arrow. Their big thing was to suck the brain energy (whatever they called it) out of other species and feed it to their fellow Devidians. We don't see any of this behavior here. And it stands to reason that other species would be victimized as well. So why don't we have any brain sucking and such in the game? It wasn't graphic in the episode -- it wouldn't have to be here. I guess I would like to se them more as they are designed and not as pew pew kill type enemies.
Now, like hippiejon a few posts back, it's my turn to plug my Foundry missions which might be more down your alley. Specifically, my Ghosts of War hexalogy (though the Devidians don't actually appear until Part III of VI).
If Cryptic does rework the Spectres arc, while they're at it they could fix its place in the Romulan Republic story sequence. For Fed and KDF players, this arc is part of the Fed-KDF war arc - but for RR players it doesn't come until after the Reman arc, which comes much later in the progression for Fed and KDF players.
The things that bothers me more with Night of the Comet is that destroying the Comet made one massive paradox. If you blow it up in the past, then the events wouldn't exist for you to be sent back into the past in the first place.
The second is that Cryptic uses the K'T'inga skin, instead of the D7 skin.
Also if they are going to revise, they have to redo TOS Drozana to match Drozana 2.0.