I'm getting confused, chapter 1 clearly shows that guns have no effect on even the weakest creatures, and clearly the people in chapter 2 are not using any sort of powers/skills/enhancements with their guns, and clearly the guns are not doing any observable damage... Why the #$%@# are guns even here? We have mages throwing fireballs, warriors using power attack skills, and tanks using barriers, but the guns make no sense whatsoever.
The above point gets even worse when you try to think about why in the living heck the PORTER has a freaking assault rifle... Why? He's a PORTER! A porter has no combat skills, their only role is to carry things, period. He has it for self defense you say? Even more stupid then, since guns have no effect! This is like having a coachman driving through dangerous firelands that carries a squirtgun for self-defense. It's absurd. The story breaks down even further when you realize that he was following the parties instructions to shoot at the giant lizard...
Things break down even more when you realize that they keep talking about monster aggro, which is a simple enough concept, typically based on monsters focusing on whoever does the most damage to it. Then you stop and realize that the mage hit it in the face with a fireball, the warrior used a power attack slash on the lizard neck, and there are at least 6 other people (not porters) firing guns at the lizard... And somehow in spite of all that, the porter presumably get one single lucky shot and gets full aggro instantly... Sigh... For this to happen in a world where aggro exists, the porter, using a weapon that's been shown to do no meaningful damage to even the WEAKEST monsters, somehow, in one bullet deals more damage than all other skill users. And this is supposed to be an experienced party 28 years after the monsters appeared, where humanity has cleared monsters out of multiple cities, so simple stupidity isn't a reasonable excuse either. Is there an explanation other than this is the world with shitty/broken game mechanics?