Jarl Skald of Dawnstar is a big opponent of the Empire. Whiterun has a high strategic importance and Balgruff is well liked by the Nordic populace.
Once Balgruff officially supports us, war should start going better for us. However, pressure should make him hurry up. What he fails to see is that his neutrality doesn’t make Ulfric weaker.
He currently just tries to keep himself out of the war thinking that he would protect his people that way. Jarl Balgruff of Whiterun is still neutral but the chance of him joining the rebellion are too small thus a replacement is not worth considering (a fact Olfrid Battleborn rejects to accept but even considering his claims might infuriate Balgruff so we will ignore him). Obviously, treacherous Jarl’s will need to be replaced with more honorable Jarls loyal to the Empire.
I think it is time to decide about who teh new Jarls should be once the Skyrim province has been restored.