I think that the wikipedia page wouldn't really dedicate much to a very fringe belief. Already they say:
Arguments against the hypothesis
There are several dating methods which contradict the theory. Observations in ancient astronomy agree with current observations with no 'phantom time' added; for example the end of the Greco-Persian Wars was marked by two solar eclipses within a year and a half; the only possible dates are 2 October 480 BCE and 14 February 478 BCE. Dating methods such as dendrochronology show that the phantom time hypothesis is incorrect, as do records of sightings of Halley's Comet. Furthermore, written records from China's Tang Dynasty, Korea's North South States Period, India's Chalukya and Chola Empires and the Rashidun Caliphate in Asia Minor coincide with the proposed missing years.
Furthermore, the University of Wisconsin labels this particular belief under the heading of Science, Pseudoscience, and Irrationalism. Georgia Tech places this idea in their "Conspiracy Theory" wiki. A google search for this idea limiting to .edu sites turns up very little, and quickly starts suggestion sites on phantom limbs (a medical phenomenon). I think it would be safe to say that this hypothesis has very little, if any, support from actual historians.
Again, just because Europe was in a very bad place during those years, doesn't mean the rest of the world was. This seems like an incredibly cultural-centric viewpoint that has no place in serious academic circles. India and China were getting along just fine in that time period, and have the documents to back it up.
So, to give you reading from the University of Wisconsin site:
Ignoring the problems of how somebody fudged the calendar, got everybody in Europe to go along, invented not just Charlemagne but entire royal lineages, and somehow got everyone to keep all their stories straight, one critic of the theory points out a fatal flaw. The theory is hopelessly Eurocentric.
For example, Mohammed either died in 614, a decade before he began dictating the Koran and 18 years before the history books say, or he lived until 929 A.D. I think we'd have spotted that already. The Phantom Time Interval completely encompasses the explosive growth of Islam. So one day it's 614 and Mohammed is an obscure visionary trader in Arabia, the next it's 911, and somehow Mohammed's ideas have spread from the Atlantic to Central Asia. And Arabs have suddenly occupied Persia and Egypt, as well as Spain, and they've been in Spain for 200 years. They've also built the Dome of the Rock in Jerusalem.
The Phantom Time interval closely approximates the Tang Dynasty of China, a high point of Chinese culture and political power. So there's a neat conspiratorial interpretation. The Tang Dynasty is an invention, a classic "golden age" myth. The only thing lacking is some explanation of how someone from medieval Europe convinced the Chinese to create a fake dynasty complete with bogus archives.
Then there are other lines of evidence. We have historical records of every appearance of Halley's Comet since 240 B.C., including Chinese records from 684, 760, and 837. The 837 approach was one of the closest and brightest ever. The Chinese were punctilious astronomical observers and modern orbital calculations match not only the dates but the positions in the sky recorded by the Chinese. 76 years x 4 = 304, not too different from the 297 years of the Phantom Time interval, except that nobody back then knew there was a comet reappearing every 76 years, so why would they have picked that interval?
The Chinese also recorded eclipses, planetary conjunctions, and even occultations of planets by the moon. During the the Tang dynasty, total solar eclipses were recorded in 756, 761, 879, and 888 and partial eclipses in 702, 729, 754, and 822. Needless to say, these observations can be checked with modern astronomical software. They really happened. Velikovsky could blow off astronomical observations by appealing to calendrical uncertainties, but there's absolutely no way you can just drop 297 years from the calendar in the last 2000 years and not notice it.
Basically it's a plain loony idea...