dvd scanning with consumer hardware is not useless, but it is HARD WORK when done properly.
First of all, scans with one single drive only tell about read error rates with that drive
Second, not all drives are useful for scanning to begin with (because they report inconsistently or have some other issues)
Third, one needs to scan with multiple drives and set limits of readability using playback testing
Fourth, testing a problematic burn of a DVD VIDEO disc using a dvd player (by viewing at the video material) is NOT a good way to see if the dvd player coped with the errors or not. MPEG-2 compression allows for a loss of great deal of information, before it is visible in the video stream. Testing should always be performed as bit accuracy / readability test (stochastic).
Fifth, scanning with a pet-darling drive like LiteOn (esp. 16xx series) can give a very misleading picture of the compatibility of the disc in other drives, because LiteOn would probably read a dvd disc even if it was pressed on camel dung. They are just so good readers. The same applies to a lesser degree to PX-716.
Sixth, one needs to understand the limits of what kind of conclusions can be drawn from the test data. Simplified conclusions like "PIE<280 in LiteOn => dvd burn within specifications" are not only inaccurate as reasoning (due to misunderstanding the facts), but can also lead to misleading conclusions about dvd compatibility. Do note the word can which is not the same as will.
As an example of how hard scanning work can be, I've just scanned c. 300 scans out of 40+ discs burned by five burners (using 8 different disc types), using seven different scanners.
The reported error rate averages and variances tell a very revealing picture of the burn quality and compatibility of the discs in a variety of devices.
However, this test has taken me over 5 weeks of continuous work to accomplish.
So, like I said, dvd scanning is HARD WORK if you want it to be accurate and useful.
Then again, if you have found out that your burners with the disc types you are using play very well on your dvd players, then be happy!
No need for you to spend long times scanning dvds.
But it does not dvd scanning useless make.