The out of network doctors were resolved the fastest for us, and the longest was the hospital stay itself, which our insurance didn't agree to pay until 8 months after the stay. It was a seriously draining experience, and luckily my wife doesn't work so I didn't have to take time off for all the phone calls and following up that was required.
I don't fault our insurer. The hospital charged more for our one night stay than another slightly further hospital recently charged us for three nights stay. It was completely ridiculous. But completely out of our hands.
I've had to deal with that and more in the last couple years. In my experience there are no "good" or "bad" guys in this fight. It's a bunch of individually rational entities that when taken as a whole are completely fucking over the rest of us.