Van dijk looks for me like the school boy who all his time has been to clever for his surroundings and couldn't flourish - now he can, in PL for Southhampton and now for Liverpool with even better players. He always lacked motivation and concentration and it still shows sometimes, but the tools have always been there. He could have done just fine and better then lenglet for us, but he wasn't an option for us when he was sold, because we needed to fill the Neymar-gab with Coutinho which in hindsight wasn't that good a deal for us. Still defense wasn't a priority, and that made sense - so i don't really feel bad of missing out on him. But it makes you think, what if played in academy for a big club, i think he would have been a ramps-great player today (career-wise).
ABout Klopp. I tottaly agree, the man is the best at team building in the whole game and his teams always plays like a unit, often with attractive football. We need him, but it would take years before he is available. He will be in liverpool for at least 3 years more.