Kind of reflecting on the series as a whole, I think the weirdest thing is that the character arc of Tang San is unclear. The fact that they started him as a innocent youth wouldn't have been much of a problem if the rest of the story was how he became an smart strategist and unflappable fighter like in the novel. At the last he has to move SOMEWHERE. The whole point of cultivation stories is the hero's journey and it's never very clear how end of the drama TS is different from beginning of the drama TS.
All the other seven devils (except XW) have pretty clear arcs, Mu Bai learns the importance of comrades, Zhu Qings learns love, Hong Jung family, Oscar bravery, Rong Rong friends. What did Tang San learn? Really don't know. He learned how to absorb soul rings better?