EGT is always higher during hard or heavy loads.
Example, Full throttle is a high load, but full throttle going up a grade is a bigger load, and having a weighed down bed and trailer is even a bigger load.
Now my F250 will hit peaks of 1600 degrees while crossing the traps at dragstrip but its only for a brief second or two then i lift after the traps and the EGTs plummet.
The new DPF trucks run as hot as 1100 degrees at idle to clean the DPF but the trucks were in theory designed to handle this abusive climate. Honestly I dont see a LDT melting down if you hit 1200-1400 degrees for short periods, now running that hot for hours up hill, yes.
A2A intercooling is your friend to reduce this issue which I have stressed as well, Im gonna figure out how to mount one on mine later this year as the water injection while it works great is going to deplete the tank to fast as another member proved, the hard part is I think im gonna have to fab a new intake manifold to have a 90 degree towards the front bumper bend to allow the intercooler plumping to fit, and then just rotate the compressor housing downward for the outlet piping.