i also might note that, for all that Karl Todbringer is a "shitty" ulrican, he oversaw the conquest and destruction of Under Middenheim, the first time in imperial history that a major skaven undercity was taken and subsequently held by imperial forces.
Meanwhile, Gunter threw away half of his provinces military strength in a futile attempt to match what we did with the iceborn flame
Actually, this is not completely correct. Under-Middenheim was taken during Karl's rule, but mainly by half of the Ulrican crusade.
Also, Gunthar didn't throw half his troops away out of arrogance. As the Ar-Ulric himself noted during his meeting with Frederick, contrary to what the rumors were saying, Gunthar's goals were actually reasonable: just the further scouring of the Middle-mountains.
It's just that things went utterly, horribly wrong for some reason.
Gunthar actually is quite a good ruler, who has done a lot of good things for Middenland, but he's just horrible at diplomacy.
The main thing he messed up is alienating Middenland's traditional powerbase (the north) by his brash and arrogant behavior.
He and his wife were too obsessed by their feeling that Middenland was losing its traditional political hegemony over the north, that they didn't realize that it often rested on the political calculations of those provinces.
Nordland has quarreled with Middenland before in Canon.
According to Torroar's post on Wulfenburg, while Ostland often supported the Wolf-emperors, they sometimes supported the Otillan emperors instead, whenever that was more expedient for them.
Ostermark was part of Talabecland for quite a while, or otherwise within its sphere of influence.
The main reason Middenland does not have any political influence on the northern trident right now is not that they sensed weakness, but that they don't trust Middenland to have their best interests in mind.