You seem familiar There's a handful of additional DLC characters -- however, they don't add more story content. They're either from V Generation, VII or from another Idea Factory title.

Here are some pointers for the DLC -- for more in-depth information please check out the links to them:
- Additional Content 1
-- Raises the level cap by 300, adds another battle to the Colosseum, a dungeon REMAKE (which just replaces the item drops or enemies), some plans to craft items, and finally a Key fragment.
- Additional Content 2
-- Same as AC1 but with fewer plans
- Additional Content 3
-- Same as AC1 but with fewer plans
- Histy's Rescue Plans
-- Adds a few plans to make leveling easier/faster
- Nepgear's Beam Zapper ZERO
-- Adds 1 new weapon for Nepgear.
- Survival Mode
-- Adds a new survival mode to the Colosseum. You survive for as long as you can and you do not regain health points after battle.
- Mini Island
-- A new dungeon is added. It introduces smaller versions of the same enemies that are weaker, but are in-turn stronger in damage.
- Lilyad Dungeon
-- Adds a new dungeon that makes Lily ranking easier.
- Shares Quests
-- Makes leveling up the shares in each nation easier with added quests to the guild.
- Babysitter's Club
-- Adds two additional characters: Compa and IF when they were kids.
- Deluxe Pack
-- Gives you access to the game's soundtrack, wallpapers + windows icons and the digital artbook.

Make sure to go over and see what content you'll want to add to your game! Be aware that once you activate the content on your save file, it cannot be undone so be careful.