I made a post previously on having rot behind a soffit and many of you gave me great advice on how to proceed in fixing it the right way.
This weekend I worked nonstop and got most of everything fixed. I removed part of soffit and cut the rafter tail to expose the area and quickly identified the problem - no kickout flashing
I cut out the rot on the sheathing and patched in plywood. I ripped the siding off all the way up to the roof to expose all the step flashing - this involved removing both the vinyl siding and the original composite siding. Working from the bottom upwards, I laid down new house wrap. I fabricated a nice piece of kick flashing to go on the end of the run.
Then I installed a nice piece of counter flashing over the step flash, then finally another layer of house wrap partially overlapping the cFlash.
I then installed pressure treated furring strips for the vinyl siding and reinstalled the siding. Here’s the siding going over my kickout flashing.
With that done I repaired the rafter tail and replaced all the rotten fascia board, then reinstalled the soffit vents.
Now I’m in the process of installing drip edge before the gutter goes back. Due to poor roof installation, the underlayment doesn’t extend down far enough to overlap my drip edge, so I’m having to cut 2.5" wide tarpaper strips and splice them in underneath the existing underlayment edge. That way the drip edge will be covered.
It is exactly as you describe!