The gasser/diesel RPM issue is entirely a Human issue...the trucks will do the work at whatever RPM they are designed to do the work just fine as long as we people get out of the trucks way, let the gas motor rev and make power.
Diesels are very nice but are not required for most pulling duties. I'm not bad mouthing diesels at all....but gas trucks do the job just fine.
One of the biggest attractions to me about a Diesel is the fact that you can fuel up in the big rig spots with ease while pulling a big trailer. I hated fueling up my gasser crew cab Dually with my 31 ft TT hitched up. They are just so busy with kids, cars, adults, etc going every way possible. Especially during summer.
Thanks,
Jeremiah