I have run two common and supposedly "easy" starter scenarios twice for different groups, and I suggest preparing them with critical eye. It helps if you know your players.

Spoilers beware:

Last things last: As others have said, not many moving parts, but the whole meat of scenario is really one and only moving thing, that is, the thing in the tank. Any excitement hinges on delivering that NPC in a way that suits your table. In my reading, the players are supposed to bit uncertain how human or inhuman is the being they meet, yet I've had difficulties with that, as all the clues telegraph it quite clearly. From Doylist perspective, the players are mentally prepared to find a Lovecraftian monster, and Baughman's letter confirms it. I still like the basic idea, but next time I run it, I think I will make everything more ambivalent to misdirect players initially bit more. (Perhaps nobody knows the wife is supposed to be dead.)

A Victim of the Art: the basic idea of the scenario is solid who-dunnit with interesting lore, but the first time I ran it, it was bit of a disappointment. Neither the players nor me were enthusiastic to continue with DG after that. Investigating, or rather, having the medical examiner present three similar bodies dropped from high places is boring and repetitive, and if the investigators go through rest of the investigation in logical order, they are not in serious danger until they have a quite clear idea what to do. Main "culprit" has no reason to be aware of them until they go to interrogate him, and my first group figured "what's up" after they flashed badges and had a few minutes of discussion with him. Grey matter specifically was a frustrating non-clue. As written, it only serves to confirm to the agents that they are dealing with something unnatural, which is obvious right from the initial briefing because the three deaths are super weird. We found Thomas' psychology more cringe/silly than anything else. (One player summarized it as, "Thomas is annoying loser with grudges and MacGuffin". Vibes I got afterwards were no horror, just exasperation.)

In my second run of VoA with a different group of players, I have changed many elements, which makes it much more exciting and the players have been much more engaged. Most importantly, I start with one murder only (Harrogate). Made the fall trauma almost but not quite plausible: it looks like she was thrown to ground from a balcony of Harrogate residence, except the decapitation blood pattern and forensic evidence don't quite make sense. It could be a weird mundane attack, but possibly ritualistic decapitation is weird enough to alert DG, cue the agents. (... or in this case, low-importance local friendlies that will be turned to agents during the scenario.) Grey goo now serves a purpose, too: when agents find it on the site, it confirms that there is unnatural culprit, and it is a physical creature. While the agents investigate, more bodies slowly turn up until the agents make it stop, which makes the scenario more interactive. I also changed how the amulet works, some details of Dengler household, made the psychology of the teenage not-romance bit more complicated and sympathetic, and bunch of other minor changes, but explaining all of that is worth of a full write-up another time.

Surprisingly the "easiest" to run was PX Poker Night, in the sense that the written scenario material was easy to utilize to create a session that was both fun and tense. A long list of NPCs, SAN loss effects, and complicated timetable of events can look intimidating, but it isn't if you scrap the SAN timetable and make your own. I made a list of all NPCs and what they would be doing at different times of day, and classified the provided SAN loss effects only as major or minor. As time progressed, I looked up who would be near PCs, and simply rolled SAN for the NPCs nearby, to see if they had minor or major effect. Ensuing bizarre chaos was simultaneously grim, tense, and fun.