Any card not mentioned here is totally fine.
Symbol of decay : Bad idea. Black has enough card decay as it is. Adding more to mill is just bad overall. And also, it's black, so why is it instant? Black shouldn't have instant spells or swift stuff, they're supposed to be really slow.
Symbol of fury : Red already has enough face damage as it is. 2 damage to the face is bad... but now you can deal 4 damage to the face with 3 mana? Blergh. Maybe the first trigger could be only 2 damage to a creature, and the second trigger only 2 damage to the face?