The last dev diary by Bob "Maurath" Hess coined a new phrase, "solofication,"
to describe how Turbine altered the Volume II epic book instances to be
made soloable. With the latest dev diary by Jonathan "Berephon" Rudder,
they may want to coin a new phrase: "skirmish-izing," a process that
has
been done to the Volume II, Book 5, Chapter 5 battle instances. To
answer the question, "why make these skirmishes?" the Turbine developer
had this to say: 

Well, the simple answer is that it was the most
logical
solution for these instances. The Battle system was pretty much a
precursor of the Skirmish system, but wasn’t scalable. With the
introduction of LOTRO's Skirmish system, it just seemed logical that we
should convert the Battles. (No, there is no current plan to convert
the Angmar Battles or the Battle of Lothlórien at this time.)

The new skirmishes play out sort of like the Siege of Gondamon
skirmish, featuring sequential assaults of several waves of mobs and
ending with a boss battle. They are playable in all the standard group
sizes (solo, duo, small fellowship, 6-man fellowship, 12-man raid) and
scale from level 55 to 65. They are repeatable, as they have always
been, but can be started from anywhere with the Skirmish Join panel
(once the player has reached that chapter of the epic books). Players
who have already beaten 2.5.5 will be "grandfathered" into the new
system, and can replay the skirmishes through the Skirmish Join panel
right away.

Rewards for these new skirmishes will be made available at
skirmish camps, and obtainable with Moria Campaign Tokens. The rewards
will be the same as current - relic and runic chests, chests of chance
- and will also remain available at the Sage of Moria standing by the
reflecting pool in the 21st Hall.

Read more details in href="http://www.lotro.com/gameinfo/devdiaries/1079-update-2-the-battle-for-moria-255-developer-diary">Update
2: The Battle for Moria: 2.5.5 Developer Diary