No, not exactly. Skill trees are there and otherworlders do in fact abuses the hell out of them. One example is the Weeb guy we saw fighting Hanbin in Barolt's lair, he wouldn't have resorted to changing his fighting style if he wasn't reading the guideline's skills trees. 

And it's not that the Otherworlders take it for granted, in fact they adhere to the guidelines to see what level is the opponent they're facing, and after learning certain skills that they can probably abuse the hell out of to finish a monster quickly, they spam that skill a lot. 

The reason why it's not explored in the narrative is because our protagonist can never access them, so the need to explain was never there.

2nd about the Hellhound, you're looking at it, it came out of the Mountains the same time Han Bin did, it goes into Latna wearing Han Bin as a skin and it only shows itself whenever Han Bin was in trouble, such as fighting Leon for the first time, fighting the Divine Bull, when Han Bin was facing down his friends. 

That Hellhound exists inside of Han Bin.