Maybe generalizing as something went wrong is the wrong way to put it, but you really don't hear the immense difference in snare between ADToE and DT12?
There is certainly a difference but I've never understood the hate it gets.
The word I always use to describe it is 'squishy'. To me it feels out of place and electronic (like from a literal electronic drum module). I know it isn't, but that's what it comes across as to me.
I think I can relate to what you're saying... from ADToE to DT12 (while both don't really have the best drum production in the whole catalogue) and the other albums there is quite a big difference.
The snare on ADToE sounds bright and very snappy, a bit thin compared to the others. If you pay attention you can hear the slight inconsistencies of the hits that make it natural and dynamic.
In DT12 it always sounds like it is hit with the exact same strength in the exact same point and gives the exact same level and tone, other than being a lot more darker and tuned lower. It definitely feels like either a trigger drum sample or a post-production augmented snare with samples.
The TGOM snare, while changing the character and the tone of the previous snare, doesn't change the feel of it. You can hear it especially on the "machine gun" sounding drum rolls and the fact that it always sounds and feels the same, no matter what.
I understand the fact that a lot of metal bands are using and have used triggers and samples to augment their snare sound and improve the consistency of the hits, I just feel that Mangini as a drummer doesn't need it to shine, nor DT needs it for the atmosphere. In my opinion it kills a bit of the vibe Mangini's playing brings when he plays live, where he is at his best.
All this IMHO, and it definitely will not stop me from totally enjoying The Astonishing when it releases. At least the master's good this time around.
EDIT: I've based my opinion of TGOM's snare on the RR track from the preorder, but you can hear it quite well on the youtube compressed version... the only thing that changes is the general tone of the mix being a bit darker and less "defined"