Not being one to leave well enough alone I had to keep digging.
So I whipped up a little spring testing gauge to see what I'm really working with.

First I tested the known-rated 12lb new spring and it tested - 12lbs!
Next, the unknown original spring and it tested - 6lbs!!
Spec says it should be 8.5lbs. It does not appear to be shortened as both ends are finished. I suppose someone may have swapped in a light spring but why leave it there if it results in light strikes?

Wolff has 8.5 and 9lbs available so I think I'll try those next to see if I can get the DA pull back into a more reasonable range.