I just wanted to chime in on tester disengagement. I am an experienced beta tester, albeit one whose experience lay mostly in an era before excellent tools like Mantis. This is an incredibly complex project to test...there are a ton of moving parts and a wealth of interlocking mechanics. This makes for a magnificently rich (And incredibly fun, I might add) player experience, however one can have trouble seeing the forest for the trees. It can be difficult to suss out exactly how the individual mechanics work on a technical level, let alone how they interact with other important systems. From the standpoint of a player this isn't really a problem...the systems simply need to work, appear to work, or simply make sense. From the perspective of a tester, and this may just be me, I want to be sure that I have at least a relatively solid grasp of a mechanic before I jump into a discussion or critique of said mechanic. This can take a good deal of time, which is why I have chosen to concentrate my early efforts on ease of use and UI issues whilst I wrap my mind around the underlying mechanics.
An example of this is my first game. I was totally wrecked by disease and a perfect storm of misfortune. (Mostly my own fault...you can read about it in the dramatic retelling I am going to post in a while.) As a new tester, I would never have guessed that there was anything wrong with the disease mechanic...everything that happened to me made reasonable sense. In retrospect it is easy for me to see that calculating disease cures before disease death would have somewhat lessened the devastation of my pandemic, but only with experience could one guess that was an issue...or knowing what, where and how to find such things within game files. This type of scenario leaves me with quite a quandary...assume that the mechanic is working as intended, or risk wasting the dev's time sorting through a mountain of issues that aren't actually issues. I will gladly err on whichever side I am told, just let me know.
P.S. It bears mentioning...I had more fun getting my arse handed to me in my first game than I have playing any 4x game, win or lose, in recent memory. As soon as I lost I immediately called my friend and recounted the tale.