I was wondering if this game is worth it for the Single-player? I've heard that there is a campaign, but is there a "random map"
mode where you can pick from a varied amount of maps? Do the DLCs contain new playable single player random maps (not campaign) or are they limited to multi-player only?
Yes, there is a skirmish option. You get around 8 maps when you buy the game. The dlc add maps for singleplayer/multiplayer and also singleplayer scenario/scenarions. All maps are usable for singleplayer and multiplayer. Campaign itself is very short and comes in to range of 6-10 hours gameplay depending on how good a player you are and first few campaign missions are basically just tutorial missions meant for those who never played a rts before.