Magpie looks extremely powerful. At first glance it looks like the money-equivalent of Herald, but since you start with 7 Treasure cards it seems like it would be much better early. It also seems excellent in engines because it can clear out treasures that might otherwise clog your deck, though in super-thin treasureless decks I imagine it's pretty useless. As a cantrip it's rarely incredibly dangerous to have in your deck, though, so it may still be useful early on even if it may eventually become useless once your deck has been trashed down. Either way, I think Magpie is going to be a very popular opener, but we'll see.
I'm not sure about Lost City. I like the concept, but it's hard to say how it will play. It obviously invites comparison to the other cards that let your opponent draw (Soothsayer, Council Room, and maybe Governor; I think that's all?). In general, you buy these cards when you need them, largely regardless of how much the draw helps your opponent. Obviously, they encourage finding a method to counter the draw (discard attacks, Possession) as well as looking for other ways to construct an engine, but at the end of the day, if you need a Council Room for draw, you get the Council Room. Lost City may behave similarly (you get it when you need a village and handsize increasers and there's no safer way to get it), but there is one key difference: your opponent gets the benefit before you. Increasing your opponents handsize by 1 hurts, but it's severely offset if you're also drawing 4 cards this turn. With Lost City, you're giving your opponent an advantage on his next turn while giving yourself no benefit until your Lost City comes up next shuffle. However, you get the benefit of Lost City throughout the game while your opponent only enjoys the benefit for one turn (though keep in mind that early turns are often the most important). For that reason, I see Lost City benefiting from long games. Also, it goes without saying that you should not fall into the same traps that many players do with Cities. If you have very few terminal actions and your Lost Cities are just Labs with an on-gain penalty, then you're probably using them wrong. Overall I really like Lost City; I think it'll be fun to see how good it turns out to be.
I really don't know much about Hero. It seems pretty good on-play, but deciding just how good it is will depend on how good the other cards in the Traveller sequence are (I'm assuming the Traveller card type just refers to the cards in that sequence). Presumably the Warrior card is incredibly powerful (it's a neat mechanic, so I assume Donald would do it justice), so I think there's a good chance that these cards are going to be worth pursuing. I am curious why it costs $5, though. Obviously it makes a difference with TfB and other cost-caring cards, but in the case of Spoils, Prizes, and such, they didn't seem to care, so I'm wondering if there's some other reason Donald wanted it to cost $5. Oh well. Looks interesting, anyhow.