Probably not as big as an issue with the DMAX's. I'm gonna say the advent of HPCR and fancy electronics and advanced injectors keep pretty good control of combustion in the cylinder.
The issue I feel would be greater, and is the same with a lot of motors especially diesels and especially larger displacements, is premature wear of bearings. Low speed idle is actually pretty hard on the bearings because there is more directional force applied versus when rotation is faster. Diesels are prone to it because of the higher compression and larger displacements are prone because of more rotating mass.
I've got my truck set to run on high idle most of the time. It eats quite a bit of fuel. I don't have any data to back up my claim... I've idled it for a longest of about 4 hours and that probably pulled 1/8th to 1/4 tank on high idle. Toasty Warm though! If its running, its usually driving a fairly long distance.
My old work truck was an 03 LB7. No high idle. It's idled/minimal low speed driving for about 200 hours during winter shutdowns. I'd say I was filling it up every 24 hours... 85 litres worth. It was quite good on fuel if you ask me. It was cresting 11000 hours and 60,000km when I left that position haha.
