Even though some of the rooms or whatever may be a bit boring/bad, most of them are really strong, and as mentioned before, they cover a wide range of desirable effects in the game
For only four ink, it can be sung by a character to deal five damage to either a location or character
Taxing effects rarely see print, and when they do, theyre either overcosted for Standard (Smothering Tithe), too little too late (Suncleanser, Eidolon of Obstruction), not relevant to the format (Damping Sphere), or just not that impactful (Tithe Taker)
The specific cards that receive Dossier treatment will likely help provide some added context to the storyline, especially when looking at the flavor text of some of these characters
Sure, they can get back Vengevines, Bloodghasts, and Gravecrawlers for free (or very cheaply), but if the opponent has a way to disrupt their creatures (and it can be as simple as several copies of Path to Exile backed by blockers), the plan of these decks suddenly fizzles