In fact he's shored up the defence to some degree by bringing in another centre back to play right back, though obviously no Samuel was always going to hurt. But looking at both the team and how it played and I don't think they had a real midfield - the team evolved over the course of the World Cup into a bit of a shambles. There was just nobody (and I really mean nobody) who I could see who was actually meant to be joining the defence (limited though it was) to the attack - Messi tried his best to do it but it meant he basically took himself out of the game by coming deep the whole time to get the ball.
Maradona completely messed up his team, it just had no balance - he needed at least one proper midfielder in there along with Mascherano to get the ball forwards to the attackers.

I'm still not a huge fan of the German defence though, Lahm aside it looks to slow and cumbersome. Loew though has clearly got his head screwed on when it comes to tactics and can go some way to covering for it without ruining his own team.