I so dearly wish this was true about game design. If it was we could just crunch a bunch of numbers and make the best game ever. But until you tell me how to quantify fun, game design will remain a fuzzy domain and one that can use numbers, but can't rely on them.
The data suggests that QoT needs to be buffed. Which buff do the numbers suggest? Increasing her health, mana, auto attack damage, spell cooldowns? Which spell do you buff? Do you need to nerf others to account for the increase in this one area? You can't tweak just one value and know what will happen. Changing on spell might completely change that character as well as change how all the other characters relate to that character!
Poke around here for a while to read more about why you can't balance by numbers, especially in a asymmetrical game: http://www.sirlin.net/.
I wanted to open with how cool the link you posted is, i bookmarked it, and it looks like i have a new read. That being said, game design does subsist in a fuzzy domain, im a philosophy major and games of abstract strategy are one of my main interests. What makes a game fun? All of us can point to examples, or sight instances, but what is the 'fun making property'? That is a scary hard question to answer and one i have put a great deal of time, thought, and study into; and i as of yet have no answer.
How to balance a pre-existing game is a different sort of question, and statistics are the answer. Pure win loss ratios can tell us where balancing needs to be done, and they can do a much better job than or own intuitions; but, as you said, not how to go about it; to do that requires a much more comprehensive set of metrics, but i believe that it is possible and that SPR's are the way to do it.
What would we need? All variable data for each demigod relative to their win/loss percentage, and a large sample. This is a very general answer; and now that you have me thinking about it i hope you will grant me some time to come up with a more precise response.
I think my [/thread closed] command is broken, but im happy that it is as now i have a new project. 