If it's going to be strong, it's going to be because of the trashing (or because you're playing alt VP). Terminal gold or gain a duchy, WITH a penalty, just isn't a very strong card, early, endgame, whenever. I mean, harvest is not so great, mandarin not that good, just, yeah, it's not so good. Gaining duchies is hardly ever something that will win you the game, except in alt VP. I'm sure chwhite will agree with me here.
So how good is the trashing? Well, the issue is, how soon can you get it. If you can spike one on a 5/2, that trashing ought to be real good. Otherwise, trashing your whole hand becomes weaker and weaker and weaker. To the point where you get to use it once, maaaaybe twice. And for a $5, it just doesn't seem that great. I mean, nice card to have sure, but I am comparing it to other 5s here. And so, the ancillary benefits make it a bit better of a card than Mandarin overall (even though mandarin is more often good, if that makes any sense), but I don't think it will be an above-average 5. Maybe I'm crazy. Maybe I'm right. Time will tell.