[MaLarsson]

I feel that it is a good practice to always check which events you want to listen to before beginning with the code.
Wowwiki has a list of all the events: http://www.wowwiki.com/Events_A-Z_(Full_List)
You can try adding something like this to your code:

local frame, events = CreateFrame("Frame", nil, UIParent), {}
 
function events:UNIT_STATS(unitID)
   if unitID == "player" then
      updateFunction()
   end
end
 
function events:COMBAT_RATING_UPDATE()
   updateFunction()
end
 
for k, v in pairs(events) do
   frame:RegisterEvent(k)
end