Since you are a club maker you probably already tried this.
Why not pull the shaft from the Walmart special and insert it into a better head if you thought it was the shaft?

Also, I have been told that steel shafts (like DGS300) actually have a "softer" frequency profile than some graphite. So I hope (and expect) you have taken this into account.

It is so hard to compare any shaft and clubhead. Are you using the same head for the comparison?

I hope this doesn't hijack your thread but:
As far as your OTT swing, from the top drop your lag elbow to your lag hip; keep the shaft inline or just above with your lag forearm then let your arms/wrists release from the forces cause by the rotation of the golf swing.

If you do the above properly you can then analyze your ball flight: If the shaft is too high above your forearm you will end up with an out-to-in path, if it is too low you will end up with a too severe in-to-out path.

Most important thing is that the lead wrist is flat!

Charles