I needed to unlock the masks because one of my ganger's is based on Mileena from Mortal Kombat, lol.
Story mode was a lot more fun than I expected. The only frustrating thing (besides occasional bugs) was the ally gang AI. It's a bit demoralising when your gang is facing 10+ enemies and also has 5 allies, but the allies just hang back on Overwatch instead of doing anything to help.
Chapter 14 was especially bad in this regard - the allies gang has two really good Heavies (one of them is Vex) who could be taking down one or two bad guys each turn, but when I played they just hid together in the top corner of the mission map, only deciding to do something useful after the nerve gas started to get really dangerous.
Now that I've played through the story mode I definitely think I would be interested in additional DLC stories, especially if there were extra maps and equipment, branching choices and special enemies like Genestealers or Bounty Hunters, etc.