I usually find myself agreeing with you rurik, but I think you're becoming intoxicated by the breadth of your football knowledge.
The football world may well understand the need for ball-playing CBs, but we're talking about the Premier League. I notice none of your examples come from here. How is it that arguably the best team in Premier League history (and an archetypal possession team) coped with a central pairing of Toure and Campbell? And how many of these essential ball-playing CBs can you name from successful sides in this league over the last decade? The truth is, the vast majority of the Premier League's best defenders are of an entirely different breed. They are physical specimens, who first and foremost excel at defending. They dominate in the air, they read the game well, and they are strong in the tackle.
It's all about context. You are talking about very technical leagues (and in particular Spain, where the technical ability is streets ahead of the Premier League). Technical ability is obviously much more of a necessity in La Liga, because that's the nature of the Spanish game. If you don't have it, you're already at a disadvantage. In England, the ferocious pace and physicality of the game require a different set of attributes. Technical players are much fewer, and are largely distributed in midfield and attack. And even then they're supplemented by Brits, who by nature are less technical and more physical. Of course, there are exceptions, but even in the modern game the majority of central defenders in this country are more brutish than exotic. It's clear that you admire Barca (and who doesn't) but it's important to remember that while we are trying to implement possession football, we are not, and never will be, a Barca clone, and we're not playing in Spain. Indeed, the most notable example of the ball-playing CB you speak of is Piqué, who was a failure here. David Luiz may yet find his feet, but he looks every bit as shaky as Piqué did here, and his languid style looks much better suited to the more rhythmic Spanish game.
Do not misunderstand me - I am not decrying the value of ball-playing CBs, or defenders with technical ability. I think they're great. But this discussion was borne from the assertion that Agger's attacking qualities somehow compensate for his defensive frailties. They don't. It's all about priorities. As far as I'm concerned, a defender in the Premier League must first be good at the fundamentals of defending. Looking sexy on the ball is of secondary importance.