Honestly, while the game is a lot of fun at the start, once you start reaching the higher chapters, there's a few spots that are stupidly difficult to pass. 11-23 was difficult, but at least manageable. 11-27 is ridiculously difficult, and unless you build a specific team for it, say goodbye to any progress in the story. Getting XP is already difficult, with how abysmally small the amount is that you get from clearing levels, so building a team from scratch is going to be ridiculously slow.