One thing that Linhenykus does demonstrate well is that fact that even very well studied and excavated areas can still yield new species. Obviously there are dinosaur localities that have had far greater attention than Bayan Mandahu, where this little guy heralds from, and show similar patterns of new discoveries and new taxa. Part of this of course is that old collections get reassessed and long buried specimens turn out to be something new and interesting but merely previously overlooked.
In this case though despite years of collecting at Bayan, by multiple long expeditions, often well manned and with lots of real specialists, we have clearly not got a complete breakdown of the dinosaurs there, and indeed there could be a lot more to find. Obviously we have great representatives of the more common material (not least Protoceratops) and there will likely be diminishing returns, but there is more to find. I’d not be surprised if there were another dozen more genera out there to turn up in the next few years and even more after that. The fact that even century plus old localities are turning up new and surprising taxa shows how far we have to go with dinosaur diversity and that it’s not just about finding new places to dig. The oldies are still goodies.
Dave Hone's Archosaur Musings 
Is it rather telling that most of these new species from heavily studied areas are either alvarezsaurs (I’m looking at you, Albertonykus) or else very small? (i.e. Fruitadens, Hesperonychus) Of course, there have been some large dinosaurs recently found in formations that have been heavily studied too (i.e. Suuwassea, Torvosaurus).
It could well be. Certainly there is a general bias in the fossil record against small species for various reasons. I’d be very intrigued to see a graph of dinosaurs discoveries over time sorted by size – it might well go down on average.
This would make sense just like the largest oilfields tend to be found first because they are easier to find.
Generally, the larger Alag Teg/Djadokhta age taxa are poorly known. We know that besides Pinacosaurus, there were hadrosaurs, sauropods, tyrannosaurs and presumably therizinosaurs (Gigantoraptor might also have lived then). Unlike the Baynshirenian and Nemegtian record, the late Campanian one is biased against large dinosaurs, although I expect some to be described and named soon.