Second zone might have some whiplash in terms of event design/heart progression, but Lowlands is so fucking good. I'm working on clearing out achievements and despite spending a good chunk of the past two weeks in that zone primarily I'm still discovering new events and things I hadn't done.
Really hoping the post-launch zones are designed more with Lolwands in mind. It has some very good verticality in its design as well, with nice use of updrafts/jumping mushrooms and actually moving rivers to "reward" folks with easier traversial using older masteries. Really liking that they're keeping that around.
I hope they do something more with the Bog Queen event/character. That's such a rad little non-boss that deserves to be a boss.