Neither of my Disk ][ drives will read any disks. I've had this problem before; replacement of the 74LS125 on the analog card solved it then. I tried a similar thing today, but the problem persisted.
For what it's worth, I noticed that the impedances of Drive 2's head are higher than they should be according to Sams Computerfacts.
Impedance on one drive shouldn't affect the other. Have you got a scope?
I'd start by working through this and seeing if you're getting signals off the various test points:
http://apple2online.com/web_documents/apple_disk_ii_technical_procedures.pdf
d.