Germany was pretty unimpressive after the 4-0 against Portugal. They are possibly the most even team, but I don't think their average is way above the average of any of the other semifinalists as you seem to imply. I am not trying to say that any of the other teams are playing excellent football, but all the supposed stars of Germany's attack (Ozil, Muller and Klose, mainly) were just average players in the last couple of games.
BTW, no defensive midfielder still in the cup is better than Mascherano, both in general and in this world cup, which has one of the hardest tasks because Argentina is the most offensive of the 4 teams.
There is also Rojo, which I did not like throught all qualifiers, but he is playing an excellent world cup on both sides of the court, thought I must say I would prefer to have Lahm or any of Brazil's excellent lateral defenders (is that the word? I do not know the English term for positions 3 and 4). Rojo is possibly on par with Kuyt, which played decently against Costa Rica.
Finally, Higuain played horribly on the first phase and on the round of 16, but last game against Belgium was clearly the best player on the match, even if you do not take into account his goal. By far a stronger play than Klose's in his last match, but of course, it is just one game.