Miki skated in a very tough era to be sure, but I dont think the era we are entering is neccessarily any easier. The Russians will send 3 very strong women to worlds practically every year, and then there is Gracie Gold who Wagner has to overcome even in her own country, and who has alot of potential to get alot better still. There are many other very promising non Russian up and comers from Miyahara, Osmond, Daleman, Edmunds, onwards. Everyone who beat Wagner at worlds minus 2 are for sure continuing, plus others who were not there; and almost all the people who beat her or finished behind her are younger and going to get alot better, which is not easily said for her.
As great as Mao is she was never the most consistent performer. Despite being quite obviously inferior Miki was always going to get some cracks at her. Beating Yu Na at worlds twice is more surprising, but in her career Worlds seems to be Yu Na's biggest nemisis event compared to Olympics, grand prix final, and everything else. Yuna wasn't 100% healthy back in 2007-08 and in 2011 she hadn't even competed all season so she was rusty and not in competition shape.