But what does the 11T lockring have to do with the chain sucking on the THREE MIDDLE GEARS as described in the first post?

Sanmano, is the Dura Ace cassete new or older? Typically you get that sort of chain suck either when the sprockets causing the trouble are older and worn to a hooked shape or if the chain is older and stretched slightly. But since you're saying that it's only an issue in three of the middle gears I'm thinking that you put in an older and fairly worn cassete.