I don't remember saying anything about DX getting less predicitble. They get less tolerant of OAT as they beat, but they fly as straight as ever with a clean hyzer flip. I've never had a DX beat up in 2 weeks, either.
I'm not convinced there's an actual mold difference between the two different tooling. I think it's just a way to distinguish between runs that molded up differently.
Let me clarify, since you presupposed your first statement for differing flight characteristics over 400' it's only fair to tell you my experience with it so far. My history with the Teebird only extends to last season. I bought a slightly used champ last year, took it out into a field, I then proceeded to throw it like my champ Eagle (20° hyzer). When it left my hand it gradually flipped up flat than it flew dead straight like it was on rails before it faded to the ground around 425'. It surprised me a little bit since it went about 25' farther than my Eagle, which I wasn't expecting. Because of the champion plastic's flight pattern, it instantly found a place in my bag.
Earlier this year I picked up a dx Teebird for the grip and the extra glide I've been hearing about. At first the disc was doing the same thing as the champ but with added glide. Within a couple weeks of using it over my champ it obtained too much high speed turn from a 20° hyzer when I throw it with maximum acceleration. Hence the landing too far right for what I need it to do. I'm not saying it can't become a 45° or more hyzer-flip disc for me, I just didn't buy it for that purpose as I have other discs that are flawless in that category.
Long story short, champion in my bag while dx is not, even though it has more glide.