I DMed the previous adventure last week with basically the same group and found this adventure a bit over-stuffed. As others have mentioned, that first encounter really doesn't do a whole lot, and neither of the necromancer encounters propel the story forward beyond saying that other groups are interested in the area--which is totally fine. But all three encounters are pretty hefty and ate up a lot of time. Even with only light role-playing at the beginning and basically blasting through the puzzle and VIMM scenes, we were almost at 7 hours. That first necromancer encounter could easily have been combined or subsumed by the second and it would have accomplished the same goal--you're not alone on the forest. While everyone enjoyed the encounters, they did feel less on task. And by the time we actually made it to the sanctum, the players were exhausted at the table. And especially since the module emphasizes how important it is to roleplay with VIMM, we needed to get there faster with fewer distractions so my players still even wanted to roleplay.
Also, unlike other BMG modules, I found this adventure to be poorly copy-edited. The first four scenes were clearly written/created by another team/maker than the last two as simple things such as bolding the enemies or indenting narrative paragraphs were completely different to the point of distraction. I know that sounds petty, but I had a really hard time making sure I knew exactly how many enemies were in those first two encounters as it wasn't clearly listed. The maps too were also a bit sprawling and sometimes weren't correctly to scale. Like several official modules, this one suffered from a lack of consistency in style that that made it feel hobbled together.
On the plus side, though, the tension in the sanctum fight was really great. And after all of the invisible spellcasters, the PCs were sure something came through other last two portals and used up several resources in making sure there wasn't anything else lurking. So that was fun to watch. The puzzle was also a lot of fun, I just wish we had gotten there earlier in the session.
All in all, the adventure was good, but by the end of it, everyone was ready to get back to the real story to the point that most of this adventure felt like filler.
[4 of 5 Stars!]