Even though Midnight Blade's first standard is called "Taijutsu Attack", it actually does both Taijutsu and Ninjutsu attribute damage. So if someone got higher Defense but lower Resistance it will deal a lot damage because it ignores that Defense. If the enemy however has higher Resistance and lower Defense than it doesn't matter at all.

Yeah that's what I thought as well at first but then I discovered that certain enemies with high resistance like Akatsuchi (in his SA where he stacks a lot of shields due to his resistance being so high) take no damage from either ninjutsu or nin-tai attacks. They're not like two seperate attack entities, they're melted together into one attack. A ninjutsu attack only effected by resistance deals about 150 damage to Akatsuchi, a nin-tai attack might do a little more like 200 or so. An attack that is pure taijutsu however deals about 12K damage to this guy.

Another example are the elemental puppets in the Ninja Exams. If you use GNW Tenten's mystery that has all attributes on it, it will hit the enemy with full power regardless of which elemental attribute the puppet is. This, in my opinion, can only be explained as the attack not being seperated by its attributes but instead counts all into one singular attack.

Edit: I guess you can take the standard puppets as an example as well. A nin-tai attack won't do only half the damage to a taijutsu puppet. As long as the taijutsu attribute is in the attack it will hit the taijutsu puppet regarless of the rest of the attributes. And it works the same as with defense and resistance. As long as the ninjutsu attribute is in the attack it will be affected by the enemies resistance, and as long as the taijutsu attribute is in the attack it will be affected by the enemies defense. If it's a nin-tai attack it will be affected by either resistance or defense, depenging on which is higher (e.g. Akatsuchi, look above)