that would simply mean that Shikamaru has a very high inteligence and that he could take out an enemy wisely. Remember the Chapter where in the Third was saying that he could have taken out Temari if Shikamaru did not surrender. that only proves hes very intelligent. And with regards to Narutos jutsu, it is as powerful as what Kakashi said. And besides, Naruto was not the one who took out kakuzu alone, Kakuzu was like vs. kakashi, shikamaru (1st part), ino (in which she did not do anything aside from locating kakuzu and hidan), chouji (whose jutsus never damaged a bit to kakuzu), then came yamato and narutos combined jutsu. so basically, it was only Hidan you went out 1 on 1. and considering the fact that Shikamaru had faced Hidan in a battle where in Asuma died. So he would have raised 1000 more plans on how to take out Hidan. Unless of course if Hidan didnot show his true abilities.