I used the exact same cable housing, ends, and cables on a different bike that has a 105 5600 groupset. On that bike the shifts are lightning fast and precise.

How should I clean and lube the RD? I read that spraying it with degreaser and then spraying some kind of lubricant on the moving parts is not the best thing to do. I took off the chain and cleaned it, it's not stretched, length is good. The rear cassette has been recently changed too.