Ah, I see.
Did you mean the jiggling was a problem with the lockring and not the crankset?

Because.

Um.

I could see the crankset jiggling when I had my bike flipped and upside down and moving the cog, not only when riding it, and my rear cog wasn't moving at all. I could feel it more while riding, but only because of the extra chainslack it and the maybe not-so-very-round-chainring caused.

Unless you're saying the jiggling crankset was destroying my hub.

Also, my lbs dude totally assured me it was my BB bearings, and not a very serious problem.