I actually enjoyed the big battles but if you were not around when they were released, they are very difficult to learn and understand without help. These days, no one needs the 2 trait points you used to earn from them so soon there may not be anyone around to help people finish those story lines.
Those class trait points are no longer granted by earning 100/200 promotion points, all class trait points are now tied to simple level-ups. However, the Epic Battle UI still references those class trait points.
In addition to that, there is a bug in Defense of Minas Tirith which was reported many years ago and has never been addressed: If grappling hooks are dismantled, it can cause the script which controls that EB to fail to advance, requiring players to abandon the instance. This bug only affects Defense of Minas Tirith.