My first impressions about the split piles: The $3 costs are really strong on both piles. Especially on the Augur pile, a singular Herb Gatherer is ridiculously strong with Sibyl. The other two cards work nicely as well, so the self synergy is very real.
The other split pile is probably not that strong, but very fun to play with. Voyage is absolutely nothing like Outpost, as being able to play 3 cards, including Treasures is a severe restriction unlike pretty much anything before. Sunken Treasure is the carrier here. I think Herbalist is legitimately good on these boards.
I already like this expansion more than Menagerie and Nocturne.