That's good, you should fix Mermaid next.
What do you think needs fixing on it?
Aside from Haven, Archive and Crypt the discarding durations thing doesn't work - you still get the next turn effect even if they're discarded from play. So you'd have to add wording to say that this cancels the duration effect or something. The problem is though, you already need a magnifying glass to read Mermaid, the text is tiny!
Mermaid is also super broken! Even as just +2 cards +2 actions -1vp isn't as bad of a drawback as Lost City's +1 card, it's pretty negligible actually. The trashing option is Masquerade + a junking attack, which is also incredibly powerful, even at $5. Unlike Ambassador you're also trashing 1 card and giving out 1, so no progress is ever made and you just pass cards back and forth until the piles run out. The duration cancelling, assume it's worded to work will never actually be chosen, because you won't touch durations in a game with this.