Vader: poor conversationalist or psychological mastermind?

A small thing that's bothered me for a while about ESB...Vader's rapid change of subject during The Great Revelation. Observe:

"If you only knew the power of the dark side. Obi-Wan never told you what happened to your father."

In the first sentence, Vader is clearly attempting to inform Luke of his ignorance of the potential of the Dark Side. However, without waiting for a response, he rapidly shifts the subject to Luke's patriarchial lineage, without establishing any connection between the two.

Was this rapid change of subject a clever ploy to keep Luke further off-balance, or is this odd incident merely the result of bad conversational habits?

 

Or was it perhaps referring to the fact that it was the power of the Dark Side that turned Anakin Skywalker into Darth Vader - this being the event that 'happened' to Anakin that Obi-Wan never told Luke about?

 

Yeah, I think he decided to give an example and just go for it.