Acheron has a variable length leash. I don't know the exact limits on it, but it's not smart to taunt the dragon, thinking that you're staying just out of range...
Roaming dragons are indeed for the win. I really like the new Acheron, though he dies easier now to massing AI (or player). Maybe it'll be perfect after unit stacking limit upgrade...
Also, I hope the team is not too busy playing Civ 5??? I for one, interestingly, have absolutely no interest in it and would rather pick up Rife 1.31.