One of the worst DLC policies I've seen for a game like this, and according to the dev, all future DLC will follow the same pattern.
Although they "add maps," what they actually do is add one-off special ops missions that are detached from the campaign. These are like preset "scenarios" that you load from the menu. The maps are not added to a randomized pool for missions. One and done, that's it. No added variety to new campaigns.
Although they "add weapons," the weapons are just given to you on purchase (pay to win) and ruin progression. They are not added to the loot pool like in a normal game, adding variety to new campaigns.
If they just did something normal instead and added variety to new campaigns, I would buy every DLC. Really odd company.