>>281380574 (OP)The author Kui apparently played through and absorbed like a dozen or more CRPGs before and while she wrote the manga. So I think in addition to her being a really good storyteller, she really understood the pros and cons of a classic dungeon crawler party and similarly really enjoyed fleshing out the world around them. You can see in the like 4 or 5 supplemental books that were released that Kui basically adores her own characters and spent considerable time understanding how they saw themselves in relation to the rest of the world as well as where the historical conflicts/prejudices/biases come from as a result.
I think as a result she never wavered too much from the main thrust of the plot and that allowed her to always get inside her characters heads. They each have prime strengths and weaknesses, they each have breaking points mentally and emotionally, they each have a prime motivation that they relate back to the rest of the group. So each member understands the other and compensates for them during low points. It's very fun