Thanks guys, I actually remembered after posting that about the Unavoidable and no counterattack thing but I still appreciate the input. I should have been more focused in my question instead of just typing a stream of consciousness because I don't think my true question was answered.
Basically what I really wanted to know is if Marked for Death affected the attack made by a Damage Barrier. Marked for Death says "all creatures gain +1 attack die when attacking this creature", so the question is, when a Damage Barrier attacks, is the creature that has the barrier making the attack or not?
Sorry for adding a bunch of stuff in that caused confusion on my actual question, especially since I remembered the answer shortly after posting... :blush: