Didn't realize Glenn didn't like FireWind. If that's true, that's too bad. I'd love to see Gus play live. I thought their last album was really good. Too bad about Chitty. Hopefully their new singer will be as good.
What about Thunderstone? What makes you think they won't play?
As for "top tier" metal bands that haven't been to the USA at all, there really aren't that many left. There was a couple of big threads about returning bands because of this and the stage times being changed this year also reflects this. There are plenty of second and third tier bands around that haven't, but the top tier headliners are in short demand without repeats. I'm still keeping my fingers crossed for Gamma Ray!