I have many Fire Beetles, they are one card not worth combining as the rental price sucks. The card has it's use in some situations!
I have not looked a Guild Brawls but as my deck is split amongst 2 accounts if a certain splinter is needed it may not work. Otherwise I may give it a go.
I am on the verge of placing ALL my cards up for rent, and then of course I won't be able to compete at all.