Right but now it’s also raining and a full moon and the goblin is a werewolf and wands also have AOE spells that hit multiple opponents, except when those opponents are blocking…

the data oriented approach works exponentially better as the object interactions become more complicated

Maybe it's just me, but I still don't see the difference. To use your example, you'd have a function like:

cast(caster, targets, weather, time, location)

or you can create an object and call it something like Spell and do something like:

class Spell

   def initialize(caster, targets, weather, time, location)
     ...
   end

   def valid_target?
     ...
   end

   def valid_caster?
     ...
   end 

end

Perhaps it's just my mental conception of things. My mental model of a class is a data structure plus a bunch of functions that implicitly take the data structure as a parameter. I realize that there can be more to it than that but it works for the purposes of this discussion.

Ultimately it's a code organization question either way. The original question is what class does it go in? Changing it to data structure + functions just changes the question to what module/file does the cast function go in? Maybe that's an easier question to answer but I guess I just don't see it.