Thanks for the feedback!
Firstly, the RNG around rare encounters is known to be painful at the moment. It works out around a 0.1% chance to encounter T-Rexaur in Balamb (since there is only 1 rare in that region). I’ve got an improvement to this coming in the next release (v1.3.0, aiming for next week). You can track that particular issue here.
Second, the point you mention around region completion is an apt one. I’ve actually got a separate piece of work on my roadmap to rework this a little, such that card collection isn’t a requirement to move passed a region (especially when it’s a grind to do so). I’ve actually created that off the back of this request.
Fortunately, the only regions that require card completion currently are Dollet and Timber. Balamb is optional (to unlock the boss), and later regions have other conditions.
Hopefully you’re enjoying the game in spite of these issues! I’m working on releasing regular changes (including new features and content, quality of life improvements, and bug fixes). Join the Discord server to get the updates first!