I'd say, if the profile is a *possible* issue, after printing with vendor color (printer manages color), you print with the vendor's *OEM profile* using the vendor paper, if that's ok then your profiled printing workflow is working, printer dialog boxes and rendering intents are correctly set, and then you print a target and profile the vendor paper, and if that doesn't compare, hey guys your have target printing issues ...oh wait that's what I wrote in my article - and no ColorSink in sight.
Vendor supplied profiles can be poor (or non existent). Bad profiles are bad profiles and with a reference image such as you recommend in the article, that's one way to evaluate if the profile is bad assuming (and that's a big assumption) all
other settings are
What I don't understand is the connection with Printer Manages Color (PMC) and Application Manages Color (AMC). Yes, if PMC looks good, you can be pretty sure the issue isn't the document data, clogged heads etc. But it doesn't necessary tell you the other path is the fault of the profile. It could be something else like a driver setting. I also don't expect PMC to match what I'd get from a good profile. If your take on this is, use PMC to ensure that the printer itself is operating OK, I'm behind you. PMC or AMC, if the printer has a clogged head or something along those lines, both processes will look poor.
In the end, you have to use a through process to uncover the issues. Is it a bad profile? Is it a bad profile and
incorrect driver settings? Is the profile OK but the user set the wrong media settings? You just have to examine all
the possible places that something can go wrong. At least with Lightroom, once you have your settings correct, the print template remembers all this, a big step in the right direction from printing out of Photoshop and other app's. You can have a prefect profile and a printer in perfect condition, everything but one item (say Media settings) can be wrong and you're getting a poor print.