ArenaNet have just released a new blog post discussing the Heart Of Maguuma. Covering four specific areas, there's a fair bit of detail here for players to digest. 

Maps With Purpose

ArenaNet have opened the lid a little bit on what players will not only first encounter when they enter the jungle but how the new content affects the game world. The blog post references Dry Top and the sandstorm that regularly sweeps through the zone. It also sounds as though this phase based shift of: Event > Reaction is much more of what ArenaNet had in mind when it comes to typical events we've previously played. 

In the deep jungles of Maguuma, you’ll run into similar stories of an even larger scale that occur in secondary phases. For example, the first map you’ll enter in Guild Wars 2: Heart of Thorns will tell the story of some of the survivors of the catastrophic Pact Fleet expedition into the jungle. Through the course of each day, the beleaguered Pact members will try to build up defenses and secure their positions so they have a chance of surviving the night—the deadly second phase of this map, when the Mordrem come out in overwhelming numbers.

Interesting and as I've previously written about, the landmass in Heart Of Thorns will be smaller than what players are perhaps expecting but the intention is to add a depth of content never seen before, across multiple levels. 

Guild Wars 2: Heart of Thorns will focus less on total land mass in the expansion and will instead focus on depth of content within that gameplay space. Each map will be rich in content, rich in 3-D play space, and very deep in replay value to ultimately provide more gameplay value to our players and not leave an empty wasteland of rarely played content behind.

Outposts

It seems as though ArenaNet have sort of merged Dynamic Events with Hearts and as we've seen in The Silverwastes, are adding specific objectives that players participate in order to accomplish a specific goal. As is the case in The Silverwastes, controlling protecting each Tower would result in a different event chain. Outposts in the Heart Of Maguuma will function similarly.

When you come across one of these outposts, you’ll find a story playing out with the NPCs and in events nearby. As you complete that outpost’s events, NPCs will be able to construct defenses, offer new services, assist you on adventures, and ultimately join in the fight against Mordremoth.

The only reservation I have about the Outpost system and we've been lead to believe it before, is that these "events" have a huge impact on the world of Tyria. It's never strictly true as the impact is only ever temporary before the whole cycle resets. I'm fine with that as the tooing and froing between you and Mordremoth's creatures is awesome, I just hope they aren't setting themselves up for a fall. 

Adventures

These sound a lot like revised Guild Challenges with the exception there's more of them and they can be played in the game world. There was, at Guild Wars 2's launch, an intention to have a variety of minigames and while there are some, they are seldom played and a little ropey. Adventures will be competative and you'll be able to see just how you stack up against other players in the game world or if neccesary, you can join together to overcome them as a group.

Your performance in adventures will be scored, and you’ll be able to see—and test yourself against—the scores of your friends and guildmates. Because adventures take place in the open world, you’ll see other players working to overcome the same challenges as you, and in many cases you’ll be able to work and excel together.

Lastly and at the tail end of the post is a little bit of information regarding "Challenging Content". There's no firm details as to what it involves other than it being everywhere but I suspect the new AI programmer they hired might have something to do with it.