All this talk about "boosted launches" and other such related off road abuse, is just that; abuse. It's brutal on a truck. CF might "have never broken anything on an auto", but I have, and I have seen plenty of carnage on automatic trucks. I got my start at 18 driving mixers. Back at that time everybody wasn't using pumps, and the concrete masons thought that a 6x6 mixer was roughly equivalent to a dozer with a barrel on it. At 18, it wasn't my truck and I was generally happy to oblige.
A dump truck shouldn't generally be doing all sorts of off roading and mud bogging, and the new AMT's, if they are what TS says, should probably do just fine in that application. The auto dumps I have seen around here don't really impress me off road. Without low range they wind up really being a slug off road, always having to boost way up with everything slipping and getting hot in the trans. The typical driver solution is to make a run at everything. The lack of low range really translates into a lack of control.
For a mixer though, I wouldn't have anything but an auto. All you do with a mixer is creep back and forth, inches at a time. The AMT might work, but I can't imagine it working well. A torque converter does have its place.
I would like a crack at driving a dump with one of those Detroit AMT's though . . .