Dragon Kills don't get updated until you finish a game. That may be why it does not look like they are counting. Also, with the recent bug fix, your new Dragon Kills stat may be less than the old Dragons Slain stat because the old stat mistakingly included hunt kills.
Hunt kills counting towards the Dragon Kills stat was a bug which we just fixed. MISIFreak - are you sure that dragon kills are not counting. Is anyone else seeing that?
The wording was "You will be eligible for the elf and dwarf when you slay 1 Black Dragon." You're right - that's not the full story. We will change it to: "You can purchase the elf and dwarf after slaying 1 Black Dragon."
Calling all Dungeoneers: We're planning some big changes and are seeking feedback. Please let us know what you think here: https://www.surveymonkey.com/r/dungeoneers_changes