it isn't that bad to work on them, true the HPOP can be a pain but not to bad, but the injectors on the 7.3 aren't a big deal to work on.
as for failures I'm guessing you mean Injector Stiction? that is usually caused by poor/incorrect maintenance & guess what their is a fix for that that doesn't require replacing them, it's a Fuel & Oil Additive Combination called "ArchOil" change the oil (inc the 3qts in the HPOP resivor), pop in that oil additive, add the fuel additive tot he tank, drive it 30-60 miles it cleans the crud that causes the stiction off , adds a hard lubricating coating to the metal surfaces, improves MPG + engine life and saves you from doing a injector job.
the only other failure(s) I can think of is the wiring harness & Injector Cups/O-Rings wich is also an issue with cummins and is only more work on a powerstroke due to the cummins only having 1 valve cover.
(Both usually caused by poor maint/normal wear)
didn't say they were new, just said they are more prone to failure from bad fuel.