My computer died Sunday afternoon and the only thing I truly miss with regard to GW2 are my friends in TEST & DoA. Something Heart of Thorns didn't really take into full consideration, it seems, is the nature of group content populations and timings; independent vs. dependent and scheduled vs. unscheduled dynamic events.
It's no great secret that MMO's are meant to be habit-forming and reward people over a period of time. So, then... what's the problem with Heart of Thorns? In one word? Variety. The new maps don't really seem like they'll thrive in the long-term, because although there is some variation, it does little to enhance the overall gameplay experience. It's a lot of waiting around to progress an area meta-event to nightfall, to Tarir, to Chak Gerent or Mouth of Mordremoth -- It's waiting to have fun, and that linear, on the rails waiting experience lacks variety which isn't conducive to an engaging experience are the Nth time. Simply put, the meta-events have very few surprises.
My main problem, personally-speaking, with Heart of Thorns is/was the lack of imagination, creativity and inspiration. The mastery system is a good place to start -- Once you've earned around 30-40 points the remaining points feel lackluster because they do little to enrich the state of the players interaction with the world/maps as much as gliding, updrafts or bouncing mushrooms. They definitely make transvering the Jungle easier, but going as far as to say the "jungle giving up its secrets" is a bit of a stretch. Are there secrets? Yes. Are they worth it? That's up to you.
I expected to go into the Maguuma Jungle and learn about the history, lore of the region -- maybe find some unique, exclusive dynamic events. Instead, anything/everything contributes exclusively to the meta-events leaving a hollow sense of foreboding. I remember being excited about maxing the lore masteries only to realize they were primarily vendor/NPC's with no unique dialog options or secret passages/mysticisms -- connections to the GW1 lore & mythology. It wouldn't have killed them to have some secret dynamic events scattered around the Maguuma. Everything felt flat and very much, "What you see is what you get".