One bit of Siege of Mirkwood™ that I have not seen discussed anywhere is how Volume II, Book 9 uses skirmishes where other books in the epic chain use instances. That they are using the new book to show off the new toy is obvious; that it has skirmishes has been discussed. No, the bit that struck me is that it does not have the group instances that all the other books have. There are solo instances to tell story bits, but it uses skirmishes instead of the old system for instanced group content.
Why does this matter? A recurring problem is how to deal with the older content for new people as the mass of the playerbase has moved past it. Most games go back a few years later and nerf content so that it solo-able, or add different grouping options, or otherwise experiment. The Lord of the Rings Online™ has weakened some content; before that it added rewards for repeating the 6-person instances so that veterans would have an incentive to help new players; and the latest talk has been of adding a “solo mode,” a mega-buff so that one player could solo what was built as a group instance.
Skirmishes get past that by building in scalability. Playing in off-hours or three years down the line? No problem: the attack on the castle has a solo difficulty built in. Small guild, or want to make it a guild event? Set it for 3, 6, or 12, or make it a higher tier. Never got into skirmishes, so your soldier is weak? You can turn down the level on many.
What impresses me is that the content has been built now so that it will be playable years from now. There will not be a need to fix it three years from now, and the grognards will have no fuel for, “Kids these days all need easy mode, while in my day we ground out ten thousand rats and liked it!” Maybe it is easier to add a super buff, but if I were the one retrofitting old instances to be solo-able, I would strongly consider turning some into skirmishes that you unlock during the epic books. This would also vastly increase the use of the content. Most people play the epic book instances once and then never look back, while people are repeating skirmishes everyday. (Making the boss fights interesting for different group sizes would be a design challenge.)