Honestly, I'd only recommend them if you really love the game. Id skip the Golden Gaffe pack, and if you only want the really challenging ones, Id stick with Rogues and Redeemers. If you play like normal, they are about 20-30 minutes a piece (at least for harder ones). Some give you different skills or classes, which make them worth replaying again. Me, Ill be buying the rest, but I will say they aren't for everyone.
Still, the spotpass maps are free, but the last one will become available in two weeks time. After that, I guess all that's left are the final spotpass teams and then the final DLC maps.