Thanks for the input. After further inspection, and another ride, I do think it is less likely the indexing is screwed up.

After more fidgeting, I got the slop to be equally distributed across all the cogs, which would indicate the cog teeth, the chain, or the derailleur. It still hits all gears, but there is a delay and rough shift in maybe 1 of 20 shifts, more commonly in the central cogs. The width of the cog teeth are down to about half their original width in the central 7 gears. Only the extreme low and high are close to the original width. I haven't measured the chain wear, but I'm assuming it must be getting time to replace that as well.

I agree with the replacing of the cables idea. I should try that too. I'm fresh out of cable and housing and have been lazy getting to the shop. Greatly appreciate the ideas. Keep em coming.