[Review not free of SPOILERS so you might want to not read this before you played it]
In my opinion, this scenario has a balancing issue. As I will try to describe, [The Wages of Sin](/card/05161) during Agenda 2 has a difficulty set on static numbers (4 heretics) who have a bit of a variable health, but that does not change their parley action or the unresolved business. Most often a scenario features a final boss with health or you have to gather clues or something else that is mostly dynamic based on the number of . Here though, the number of Heretics is 4 period.
In my experience, it is possible to get all 4 Heretics down with a highly specialized duo and a bit of luck, so I did it with [Rita Young](/card/05005) and [Ursula Downs](/card/04002) and 2 [Shortcut](/card/03232) on the VP Locations. With all the free moves of [Rita Young](/card/05005) and her combat strength on the one hand and [Ursula Downs](/card/04002)' free investigates on the other hand I was able to get all 4 Heretics but usually with investigators, 2 seems to be a good result. with 4 Investigators, you could reasonably hope for 3-4 while with one investigator you have a hard time to get just 1.
Now, having that said, this scenario is often compared to [Undimensioned and Unseen](/card/02236) which in my opinion is not completely true, since [Undimensioned and Unseen](/card/02236) provides the investigators with a map that makes it easier to move around and plan, the opponents come one by another and their health (which is tied to ) is the only obstacle, you have to defeat them and you are done, there is no Unfinished Business, so in my experience, it is manageable, even solo. Basically you have to have patience with [Undimensioned and Unseen](/card/02236) and wait for the best moment to strike and you actually have a good chunk of time. Now with [The Wages of Sin](/card/05161), this is not true, you have almost no time to gather the 3 Clues to even start the work to be done, and than very soon you will be plagued by [The Spectral Watcher](/card/05086), Haunting abilities, a very punishing spectral encounter deck, especially those enemies that die only of specific weapons and than on top of it all, you are dealing with the Heretic's effects once they are defeated (their Unfinished Business)- punishing you and also requires you to even fulfill others tasks that requires moving, clueing and sometimes fighting.
Also it should be considered, that the number of Heretics is fixed, so while playing with 4 Investigators, looking at the other side of the Heretic's cards is way more easy, especially since it always just costs 1 Clue. You get 4 Encounter Cards a round, that's true, but to fulfill the Heretics Unfinished Businesses you need to plan and intel provided by parleying helps a lot. Getting swarmed while an Unfinished Business is active while solo could possibly cost you the game.
In a nutshell, with my experience, information I gathered by watching youtubers trying it and also expereinces shared by friends I cane to the conclusion that the more investigators you are having here, the more easy it gets. If you have specialized builds for this, at it becomes to easy (even though I doubt it) you can always play on hard difficulty but compensating difficulty with more players is not to my liking.
In my opinion this can and should be fixed by manipulating [Death's Approach](/card/05163), that's why I am writing the review here. This scenario is difficult though playable, if you do have enough time. 7 doom after [The Spectral Watcher](/card/05086) appears is way to low for smaller groups because of the many static parts of the scenario. So a suggestion, this card should have something like the following text added.
"this card gains an additional doom threshold of 8-2"
So, as solo player you have 13 turns, 2 players have 11 turns and so on. While most scenarios have there inherent difficulty dynamic (like deal damage, get clues etc.) with the number of investigators and a (mostly) static amount of time (i.e. doom), in this scenario the inherent difficulty is (mostly) static (i.e. number of Heretics in play) so the available amount of time should be dynamic (based on )