Maybe you shouldn't be so rigid as far as having ALL wheels in-gauge?
Seems to me that compromise can be a good thing, and that trying to get a 2-6-6-2 through all possible combinations of track and turnouts IN N-SCALE means that maybe Bachmann knew what they were doing to some degree.
And I take exception to the claim that they don't reply, as I have found that when communicating with Bachmann you only have to be courteous and try to allow for their corporate system. And not be unreasonable. Keep in mind that a service tech is too highly paid to just put them on the phone whenever someone has a problem, so you have to work your way down the list.
Their customer service is rather highly rated compared to other Nscale companies, unless you're one of those impossible-to-please people.
Visit their discussion forum and try to engage both the members and the moderator known as The Bach-Man himself in your situation.
Also, there are some ongoing topics about your locomotive at the Atlas N forum.
The 2-6-6-2 has some minor issues, but nothing like what you're describing and that may be because you think all of the wheelsets MUST be in-gauge.
So many axles in a model that small means there has to be some "wiggle-room" for it to operate reliably over both good and bad track.
Lighten up, because they're not trying to screw you, and as far as nobody "Liking" your original post, I imagine what's really going on is that no members of this small Nscale forum even HAVE the same loco and therefore have no advice for you.
Go to Bachmann's and Atlas's forums where the 2-6-6-2 is actually a current topic among several members, and good luck.
I hope you get it running to your satisfaction.