The DLC is quite good, you get some quite good additional units, like these SpotPass units but with some special abilities and new artwork.
There are three DLC maps where you easily get money, experience and additional sacred/rare weapons.
And there are too DLC only classes, Bride, which uses bows, lances and staves, and Demon Knight, which uses swords , axes and tomes.
In that hard DLC all enemy units have all stats capped, Dragonscale as ability and their stat caps are ridiculously high too.