What are Skirmishes, and how will they work?
The Skirmish system will allow all players -- raiders, casuals, mid-level, high-level -- access to the same content.
Twelve new Skirmish instances will be available in addition to a pair of tutorial instances designed to introduce players to the system. Each of these instances is scalable based on the number of players; they each accept one, three, six, or twelve players at a time, with the deficit made up for by player-created NPC soldiers- to make a grand total of 24. Additionally, many of the instances are scalable by level; for instance, one skirmish which features an assault upon and defense of Weathertop will accept players from level 30 to 65. Each instance has nine optional challenges, each of which awards skirmish points -- more on those in a moment. These challenges are randomized, as are the enemies inside the instance (within certain logical limits, of course), so you will not likely have the same experience twice.
For example, Jeffrey Steefel demoed the opening of one of these Skirmishes in which a number of NPCs have been locked within the Prancing Pony, and Sharkey's men are threatening to burn it down. Your job is to defend the Bree-town landmark. The Pony itself has hit points during this Skirmish, and you are awarded Skirmish points based upon how well you defend the Pony. Let the building's hit points fall to zero and you fail your primary objective.
Now, Skirmish points: These are your rewards for completing your challenges -- primary and optional -- in each instance. They can be used to customize and advance your soldiers. Soldiers are quite customizable: You can assign them traits, just like a player character, and you can alter their cosmetic appearance. The Skirmish point system will even be tied into MyLOTRO, where there will be leaderboards on which you can compare yourself to your friends.
You can enter a Skirmish from anywhere in the game world, as can your friends from their own locations in the game world. When you're done with the Skirmish -- each of them is designed to last thirty to forty minutes -- you will be transported back to your prior location in the world. [source]
Each player has 1 Soldier. A group of 12 doing an instance would have 12 Soldiers total. So the player group would be leading the equivalent of a second raid group in the 12 mans. Though each player would only have control of their own soldier. And yes, you can still use any pets/banners you would normally have in addition to your soldier. [source]
Skirmishes reward experience-points, complimenting the level up experience, and can be accessed as low as level 30. [source]
Skirmishes are PvE, and should not be directly competing with PvMP. [source]
Skirmishes are not session play. [source]
What is "Enhanced Combat Responsiveness"?
Here is a quick explanation from Floon:
Autoattacks will not delay firing a skill. What this does mean is that animation have a chance to preempt autoattack anims in such a way as to produce a pop in the anim transition that isn't there right now. [source]
What is "World Join"?
Zombie Columbus goes in to details about what it is, and what it will actually be called:
World-join is a bit of a misnomer. The name of that part of the overall Skirmish system is likely being changed to the more informative "Skirmish-join." Remember the way half the community calls Fellowship Maneouvers Conjunctions because that's what it was in beta? This is one of those situations.
Well, what IS Skirmish-join? There will be a dev diary on it (I'm working on it now) but the short version is it will be how players can enter the new Skirmish spaces. It's a UI that will allow players to select the group size, level, and difficulty of a Skirmish, and then be instantly transported to the Skirmish. Emphasis on "Skirmish", the system does not, as of now, interact with Instances, PvMP, Battle Instances or anything else. [source]