Dual-wheel method showed the hanger a bit off, which I believe I corrected.
I'll hunt around for the tool, but until then I'm ruling the hanger aligned.

But, the RD is still not dropping the chain onto the small cog, messing up all other smaller cog shifting. I even lengthened the cable housing entering the DR, to decrease friction, just in case that had any affect.

How's this for a possibility? The top jockey wheel is so close to the 12t cog that chain stiffness slows or prevents the final shift?