Just keep it with the original game and the experimental DLC of it. This stand-alone 'sequel' is just a disappointment. It looks and plays great, but the campaign gets tiresome just too fast: you've to replay the same three (desert) maps three times in the same way as you did before. I got exhausted with the campaign not even half-way into it.
It would have been OK if the player - with every revisit of the map - would start on a different spot or had to do something else. In that way, the egregious lack of content and creativity would not have been this obvious. Perhaps it was the narrative that forced the game desingers to create the sense of 'being stuck in limbo', but that is no excuse for making the gameplay so tedious.
That is why I like the arcade mode more. It has twice the amount of maps, no repeating cutscenes and no repeating objectives; just simple, non-stop action. However, with all the survival games out on Steam (including Killing Floor 2) I don't see much reason for anyone to spent more than 2 bucks on this skimpy game.