Well, I have been away, and I find this has been a quite interesting discussion.
Now I realize that no one responding knows the actual job conditions, but in my experience, when stripping for a dredge, it will be very wet material. You likely will not be able to work from the bottom of the cut, but will need to dig down from the top, Thereby making the excavator the machine of choice. The difference of loading trucks on the same level, or loading them below the excavator in the bottom of the cut can make a difference of 25% or more in the production. In my experience, loading 35 ton artics with a 375 Cat, loading at the same level we were getting 200 to 220 loads per shift, but in the same material, when we were able to get trucks into the bottom, it went up to the 280 load range, an increase of over 30%. So many variables that you can only guess unless you know the actual site conditions. Scrapers work great, but in the mud, an artic will haul a full load every trip, and will run in muck clear past the axles. In these conditions, a scraper is pretty much helpless.
Regarding the production estimate on the EX-1200, I have read the article, and seen the pictures, and he is digging relatively hard material from a depth of 25 ft below the machine, and due to the conditions, swinging nearly 180* to load trucks. This is also digging underwater, where fill factor for the bucket is less. This machine in optimum conditions would probably dig 1/2 again that much.
Another consideration is that if the ground conditions are poor, it may not support a 385 size machine. A lot of operations in the southern states use a 400 with wide tracks for this reason.
Consider the safety aspect of dumping into a 100 ft deep dredged pit. Is it full of water, if so, it is even more unstable. You need to dump trucks away from this edge and push it out with a dozer, probably a wide track. Always leave a good high berm so the dozer or trucks do not become part of the fill.
The rigid frame trucks mentioned are the best when conditions are good, but I suspect if this material is unstable, they will be stuck more than they will be hauling.
Once again, I do not know the actual site conditions, but a blanket statement of what will work is no good without more information.
I also want to twist the comment "A loader will outload an excavator"
What size loader?
What kind of material?
Loading at grade or below grade?
Loose stockpile or tight bank?
Plenty of room, or tight quarters?
In my experience, if you compare by machine weight, the loader wins, but if you compare by bucket size the excavator wins.
Example:
988B loader (100,000#) will outload a 350 excavator (100,000#),
but 375 excavator with 7.5cy bucket will outload 988B with 7.5cy bucket
I'll quit using up space now
JD