Re: Cultist chaining, its no better than Familiar chaining really. You get the +2 cards instead of +1 card, but the additional "cursing" (or ruinating, I should say, to coin a word) action is conditional on drawing another Cultists.
BUT its a lot less disruptive to your tempo to seek Cultist than Familiar, as $5 is easier to get to than $3P, what with Horse Traders etc, and $5 remains more useful in the later game than $3P. Familiar is very often bypassable on a fast Kingdom - while they arse around getting the potion then the familiar, you can Hunting Party-Gold or FishingVillage-Wharf or whatever to victory. In contrast, a $5 Cultist disrupts your tempo a lot less, and has the side effect of inflicting diversity in an opposing deck, which is weak if they're using fairgrounds or menageries, but strong if they're playing Hunting Parties. In fact, I'm confident that a Cultist or two will demolish a traditional Hunting Party rush deck.
Then, of course, there's the trashing effect, which is an awesome little bonus. One of the main worries with Familiar is that once the curses run out, you're left with a card that does nothing. Sure, if you draw it with an action in hand, you can cycle it, but if you draw it on a terminal draw, its a dead card. Familiar really benefits from a trash-for-benefit buddy to work with. Cultist, otoh, needs just any trashing card to make it trash-for-benefit, and given that you'll likely want the trasher to get rid of ruins anyway, that makes Cultist + Any Trasher a fantastic combo.
On the downside, Cultist is an attack that works strongly in engines, I think, but the very nature of its attack will make engine building harder (a bit like Mountebank or Witch, in that sense). That makes me think that 2 Cultists + BM might be better than trying to build Cultists + most Engines, unless there's Chapels and Fishing Villages and Wharfs and other super strong stuff like that.
Overall I'd rate Cultist as a top tier card, almost up there with the other strong $5 attacks, like Mountebank and Witch. Well, perhaps equal with Witch, and marginally worse than Mountebank. But definitely better than Saboteur, and superior to Familiar by virtue of its cost and built in trash for benefit.