RCLootCouncil author here.

For your Classic version, in TitanSocial.lua line 102 you're calling _G.GetNumClasses() - that doesn't exist in Classic, and would normally prevent the for loop from doing anything. I reimplemented it for the Classic version of RCLootCouncil, in which it simply returns _G.MAX_CLASSES, i.e. the loop gets run.

This results in the call to GetClassInfo() which also doesn't exist in Classic, but which I've also reimplemented with the proper calls to C_CreatureInfo.GetClassInfo() which they kindly kept.

So basically your code should work, as I've reimplemented the missing functions - but of course Blizzard isn't that easy to work with. They left a gap in the class list because Death Knights have ID 6, which causes TitanSocial to use a nil as a table index. You can check with something like:

for i = 1, GetNumClasses() do
   print(GetClassInfo(i))
end

I suggest you do something for the Classic version (as the current implementation normally does nothing) or simply check for nils before updating the table. Do note _G.MAX_CLASSES is 10 (as excepted) but druids have ID 11 in C_CreatureInfo.GetClassInfo().

Thanks for the details!