Besides anecdotal player feedback from respected veteran players, what data are the devs collecting to help with balance decisions? Can they tell which units are most often used to strike the killing blow, for example?
Vet players could tell you that. Besides that, they technically said they have access to the servers, so they can probably inertly collect data like that. However, just the sheer number of "beta testers" should kind of guide that by default. You could argue the quality of the beta testers, but it is often impolite to do that to indie games who use an open beta.
At the moment, very little, other than games played. It's high on our priority to start actually be able to gather more gameplay data. Once we have a more meaty bit of information to share, we will. It's incredibly important to us to get data. Anecdotes are great, but seeing who's actually using what during the course of normal gameplay really answers a lot of questions. More information will be coming soon on this topic, and a few related ones. Good timing on the topic.
I have plan to set up a web page to evaluate the balance of PA using different metrics. We'll see how far I'll get with it.