Man, this was a tough one! The goal in this mission is to find and defeat Strahd once and for all by destroying both him and all of his potential resting places (coffins). Like much of Castle Ravenloft, there are some aspects of the rules that are confusing. Some of the interpretive issues we struggled with were:
(1) Does the victory condition of "destroy all of the Coffins" mean only all of the Coffins that have already been placed when Strahd is defeated or does it require that you keep turning over tiles until you've placed all of the coffins? The Wife and I disagreed on this point, but due to the strategy we eventually chose it was a moot point because we ended up with all the coffins on the board anyway.
(2) When you reveal Strahd's Crypt, what does the "If Strahd is not in play" condition mean? Does it apply only if the "Strahd Appears" coffin hasn't been found or does it apply if that coffin has been found and Strahd has been knocked to lower than 5 hp and reduced to mist?
(3) What happens if you turn over enough tiles to get Strahd's Crypt to appear without opening any coffins and then defeat Strahd? The text says Strahd "makes his last stand from his crypt", but if you then subsequently turn over the coffin that says "Strahd Appears", do you have to go through it all again?
Our first couple of tries, we proceeded by turning over tiles and destroying the coffins as soon as they appeared. This led, each time, to Strahd appearing fairly early and would have required us to basically defeat him twice (once to get him to turn to mist so we could survive long enough to turn over all of the coffins, and a second time after placing the Strahd's Crypt tile when he returns to full hp). We actually came very close to succeeding on this method, but still died both times.
We then tried a different strategy for the next couple of attempts, and this was to turn over tiles without destroying coffins, then defeat Strahd when the "Strahd's Crypt" tile appeared, and then destroy all the coffins (ignoring the one that said "Strahd Appears" on the theory he had already made his "last stand from his crypt"). This too got us defeated twice in a row.
For our fifth and barely successful attempt (which was somewhat arguable because a phone call in the middle of the game left us unsure about a crucial action), we followed the same strategy as our third and fourth attempts.
We were happy to have finally won after so many defeats, but the unclear nature of the victory conditions left it somewhat unsatisfying as we're still not 100% sure whether we ran the adventure as it was intended.
Anyway, looking online it appears there are two official bonus scenarios which we plan to play sometime in the future . . .