Runes might be belong to the giants but (because of their language, script and surely their culture) dwarves are best suited basic race for a rune theme. Then, the goliaths of course.
Well, i did not watch last season but dnd is much more combat oriented. Different systems would be so much better for games like Stranger Things. Little Fears system could be nice even World of Darkness could be great (without any vampires, hunters, werewlves etc but just pure setting details)
In first look Berserker looks strong. But actually (as you mentioned) Berserker is just for combat oriented. When party meets with different encounters like social, skilll based, stealth, lore, search etc it is completely useless.
And secondly, monk is not good match up for barbarian. Most...