You could use that logic to defend any terrible, no-fun card as long as it was unique. Yeah Courser is academically interesting and it's one card out of 500 or whatever, but that doesn't mean it's worth making if games with it are mostly bad. And to be clear I'm not defending Mountebank, though personally I tend to like Mountebank games fine these days.
With Courser, I must admit that I wanted urm, some kind of “feels bad, man” card into this set. Not unlike Mountebank that I previously mentioned. I want players to be like “
Okay, so Curses are truly going to be an issue here. So think, my dude, think! Should I trash them at the risk of being re-Cursed, or hold onto the 5 Curses I’ve been given and roll with a less optimised deck anyway?”. These kinds of mental preparations are pretty unique to Courser games and that’s the sort of intriguing meta I was aiming for.
Uh. In Dominion, there are also cards like Wall and Bandit Fort, which, to me, makes games dreadful and not very fun. But! I accept their presence and hey, the game doesn’t completely break when they’re there. Likewise, I don’t think Courser breaks Dominion. It does make you go “aww shite” indeed, but it ain’t, in my opinion, so offensive that it has no right to exist.
It takes a bunch of work to get Hoarder up to being able to gain Provinces even on boards where it is possible, so I don't necessarily think it is overpowered; there are other Province-gaining combos after all. Something that could be a problem though is that it's best with the two mixed piles - Castles and Knights - and those can easily lead to situations where one player is able to play Hoarder for Provinces and the others aren't because the only Action-Victory cards got sniped.
I thought of these piles being problematic, but came at peace with them when I pondered on how they would play with Hoarders.
The Castle-pile, first of all, is ordered in a specific way; which means you know what to expect, you know what you’ll be revealing for your opponent(s). You can plan to try not to reveal Small Castle and Opulent Castle – you’re in control of that. Um. For Humble Castle, though, I suppose it’s 1st player advantage to grab it. But it ain’t a very good opening, at least. In games with more than 2 players, this problem becomes even less apparent, because there is an extra copy of these 3-typed Castles anyway.
As for the Knights, only Dame Josephine gives you 4 types in one. The Victory tag is the extra type you want for Hoarder. But! It’s risky, because Dame Josephine can be trashed by another Knight anyway. So the investment is pretty unsafe and
can be broken. Therefore, I don’t believe it’s too unfair if you managed to snipe her. Besides, she’s pretty bad as a Knight.