RotK 13, How to fight against Coalitions?

I have been having trouble fighting against Coalitions since I bought the game. Somewhere around 15-20 years into a game, one faction will call a coalition on my faction and everyone will join.

This wasn't a problem in previous games where you could reduce the avenues of attack. But now I am being attacked from everywhere. This wouldn't be so bad, but some enemy forces are outright suicidal in their obsession with attacking me. I cannot shift forces from one front to another at all because certain forces will just keep cobbling together weak forces to come at me again. I am left wondering "Does this only end when I have nothing left?"

To make matters worse I am experiencing these campaigns where my faction is fighting on 4 fronts and winning on 3 out of 4 and I start getting a chain of messages that officers on my side have started dying on the one front I am losing and yet I am getting no messages that enemy officers are dying at all. It's like they can just keep coming at me with their ill conceived zerg rushes with no real consequence while my side loses precious officers over and over again.

It gets so dispiriting that I have quit my first two campaigns. The first was one as Zhao Yun, where Cao Cao called a coalition against Liu Bei and Liu Biao and Liu Zhang joined him and Ma Teng against us (setting was Historical). The second time was as Xiahou Dun where Yuan Shao called coalition against us, and Liu Biao, Sun Ce, and Ma Teng sided together to help him against us. In that one I was a viceroy and thoroughly crushed Liu Biao's armies, only to see him raise 6k here and 5k there over and over again, for almost a year straight, while I watched notification after notification of Sun Ce's force killing all the officers in the District to the east of me (and slowly taking all the cities over there to open another front I will have to defend with the zero officers I have left to deploy) all I could do was watch as this never ending nightmare just continued.

I guess those are my questions, how do you defend against that? and what's the calculation behind 3-4 of my officers dying every quarter of a year in one front, while 0 enemy officers died in the other 3 fronts we were winning?