You guys underestimated Minato. As I can remember, Minato defeated enemies in a flash..How can he show us other powerful jutsus when he can take out enemies with a kunai or a rasengan? Is there a need for him to use powerful techniques? Even Tobi retreated after being hit with a rasengan. It does not mean that he don't have any powerful techniques because being a genius, and someone that can create S-rank jutsus simply means that he is capable of creating jutsus lower than an S-rank. In his very short appearance in the manga, he showed us these jutsus:
Dead Demon Consuming Seal
Eight Trigrams Sealing Style
Flying Thunder God Technique
Four Symbols Seal
Rasengan
Space–Time Barrier
Summoning Technique (Toads)
Summoning: Food Cart Destroyer Technique
Now, can anyone provide another character capable of displaying more jutsus than Minato in a very short appearance in this manga? Hiruzen was called the professor, a master of all Konoha's existing techniques at his time yet we only saw him perform these techs:
Dead Demon Consuming Seal
Earth Release: Earth-Style Wall
Fire Release: Fire Dragon Flame Bullet
Shadow Clone Technique
Shuriken Shadow Clone Technique
Summoning Technique (Monkey King: Enma)
Telescope Technique
Based on Hiruzen's jutsu's we've seen so far, can we conclude that these are the only techniques he knows?