This is as much an attempt to make sure I have my own thoughts sorted out straight as it is to explain them to anyone else, really, because a lot of my opinions on canon are kind of pulling in tidbits from a lot of other places and throwing it all at the wall and seeing what sticks.
The entire issue of the northern campaigns is slightly problematic in characterizing Jiang Wei. It's the main reason he's a controversial figure in actual history, and it's...a little weird to reconcile with his portrayal in Shu mode in some ways, even if it lines up okay in others. Historically, there has been an assload of debate about whether Jiang Wei was a good general or not, and the bottom line in a lot of it seems to come down to that one big question:
What the
hell was he thinking?
( a bunch of wordvomit of speculation kind of vaguely based in history i guess? )