JNPR is actually one of the best anti-army teams available: Jaune has a lot of Aura, and doesn't know what his Semblance is; this means that he can just use all of his Aura for defense, making him one of the best endurance fighters. Combine this with his shield letting him block hits without using his Aura, and him being the best out of the first-years at fighting without using Aura or Semblance, and he can theoretically keep going longer than anyone else on teams RWBY and JNPR. Pyrrha can use her Semblance to compensate for any of the group getting sloppy as the fight drags on, and she can keep her Aura up a long time against the Grimm (they don't have any metal weapons for her to use her “Polarity” Semblance on, and she can block hits with her shield). Not only that, her Semblance is perfectly suited to fighting in an urban environment, and she can weaponise literally the entire city if push comes to shove. Nora is basically an Area over Effect specialist, considering she wields a combination war hammer/grenade launcher. This makes her especially suited to taking out large groups of Grimm. Ren will likely become more dangerous as the fight drags on, once he runs out of ammo. Considering that he seems to be the best out of the first-years at weaponizing his Aura, he can just switch to tearing Grimm apart with his bare hands when his weapons are dry.