I think you get some decent items if you help him too, though I cant swear to it.
I found build to be a worthless stat all around, it doesn't give a significant amount of hp next to +hp items. Once Rada transforms she became an insanely good tank, she cant be hit, has huge hp and hits really hard (and fast I think)
I went pure int on victor and telle, for big fights i want to be able to spam my heavy hitters as often as possible. Air shackles looks great for bosses, which can be incredibly tough
Chests are definitely worth it, some of my best weapons have come from them. they seem to give loot for your level though, so at a low level you're going to get meh items.
Id does get repetitive to kill an area for not other reason than exp, but it feels so rewarding when I find a group of rats