Metrics just means information games store to be reviewed by the developers. They're everywhere anymore. The amount of time you spend looking at the store per hour played on Farmville is reported directly. How many random thugs you beat up between story missions on Arkham City is stored. Metrics measure just about everything in most big budget games and if you play anywhere near an internet connection its being uploaded to the developers.
The introduction of metrics into modern gaming is interesting. Now the more hours I log riding aimlessly around in Red Dead will encourage the next game to be even more open. It also has its problems- http://penny-arcade.com/patv/episode/metrics sums it up better than I can if you're into that kind of thing. None of this paragraph's tangent has anything to do with my question:
What kind of metrics are you keeping in DD? Do you know how often players use certain items, gods, or classes? At first I thought of asking because I was a little ashamed when I discovered some of my more glaring play errors, and more so when I thought about how many more I haven't discovered yet. I imagined devs face palming and laughing over popcorn while I miss-clicked and died to popcorn.
Anyways, seems like a very helpful tool that merited discussion.