I don't think any Tales game has good writing either. However, if you compare Symphonia to Zestiria, the latter is just more all-around fleshed out. Skits are more numerous, imaginative and generally funnier; Symphonia's skits are mostly dull and bare-bones. Dialogue and characterization are generally more fleshed out in Zestiria too. Same for the combat/character development system, side quests, etc. Symphonia's writing and design feels like the devs were still learning the ropes.
One could argue some systems in Zestiria are needlessly overcomplicated (i.e. just added for the sake of being there but not really that useful or interesting), but Symphonia's by contrast are fairly primitive.
Also, regarding that plotline: yes, you bury him later. Still, the situation struck me as unexpectedly creepy in and of itself, even compared to the human farm and other plotlines. Perhaps a bit over the top so. And yeah, neither the characters - nor, I would say, the game's writers - knew what to do about it. In a way, this is a typical JRPG dissonance between dark motifs/plotlines and cheerful aesthetics/attitude, it's just that it can be less or, like in this case, more jarring.
Also if you manage to beat an 'unwinnable' fight early on, you get a L3 Ex. Gem that unlocks some great skills long before you can find one normally.
Yeah, that was a good fight. I beat it, but only barely and by burning through all my consumables.
Didn't know about the rest of the things you mentioned.
