The common consensus seems to indicate that the formations from the Death masque set are below par, especially the troupe replacements.
I am currently building a list at 1850 points, running a standard Revenge formation, and am toying with the idea of adding the Death's Companions in a Cast of Players alongside.
Like the rest of the army, they will be able to run and charge the same turn. In addition, they can use their ability turn one, and also benefit from Crusader, making them extremely fast for a unit on foot.
The main problems are the mandatory upgrades. However, the two kisses and two Caresses are similar to what I would take in a standard troupe. In fact, building a troupe with similar upgrades is 11 points MORE expensive than the Death's Companions. That is without the neuro disruptor, which they get on top of that, but that I ignored since it is trivial in the game. The only downside that matters in that respect is the weakened troupe master (Dusk has -1 WS, -1 BS, -1 I, and -1 A).
The way I see it, running a Death's Companion in a Cast of Players gives you more for less.