Since I love performing sidewalk analysis on others, my two bits on Yagudin/Mishin/Tarasova and Plusehnko/Mishin.
I think there was a pseduo father/son relationship between Mishin and his two star pupils. Yagudin as the elder (jealous of the doting attention his younger sibling was receiving) began rebelling against dad and acting out in inappropriate ways. It fell to younger, favored son Plushenko to show unquestioning loyalty (which he certainly did).
Basically, Yagudin had had enough male firmness and wanted some female leniency which he found in Tarasova. In one interview he referred to her as a 'typical Russian granny' which said a lot. Where Mishin was demanding and unyielding, Tarasova was permissive and forgiving (though fully capable of ripping him a new one when he needed it).
Yagudin had all the jumps by the time he left Mishin and was boring as dishwater to watch. It was only with Tarasova that he became a great all round skater.
Plushenko, I don't think ever really has. He absolutely won in Turin in both SP and LP but even his biggest fans were excited by his winning and not by any particular aspect of his actual performances which were workmanlike and uninspired.
If I were a 6.0 judge, I would have had him first in both SP and LP but I enjoyed Weir's SP more (a lot) and about six other men's LPs more.
As for his potential comeback. All in all I had the impression that as the years ticked off, Plushenko was having to give up more and more non-jumping elements in order to keep the jumps (which also were beginning to fray a little, the salchow had actually become a problem jump for him).
I think show skating is really the better option for him at this point, he doesn't need as much jump content and can let some expression out (look at how much more interesting his Turin exhibition was in comparison with the competition).
If he comes back and is as overmarked as he was in Turin twice (I'll give the judges a pass on his first competition) I'll be seriously bummed.