I've never heard of the Vault of the Dracolich
Many haven't. I could write a whole thing on how some of the best
ever (IMO) WotC-written adventures happened during "the interregnum" (as I like to call it) - the space
between 4e and 5e. The trouble is, none of them were marketed for sale. They were given to WPN stores and used at conventions. Mostly to playtest 5e.
They are, if I remember, Legacy of the Crystal Shard, Murder at Baldur's Gate, Vault of the Dracolich, Ghosts of Dragonspear Castle, Scourge of the Sword Coast, and Dead In Thay.
The most famous ones are Ghosts of Dragonspear Castle, I think because it was given away at GenCon in large quantities, and Dead In Thay because it appears in 5e in Tales of the Yawning Portal.
Those two are the WEAKEST of them. GoDC because it's really unpolished compared to the others, and Dead In Thay because (at least to me) it's not very exciting - it's just a big weird dungeon without much story.
The others are really great.