I have the feeling, that with a rainbow denial, your opponent will speed up more than yourself.
The other traditional denial decks will become trios if you want to add shard of bravery.
If I want to add shard of bravery to denial, the first thing that comes upp to my mind are quicksand golems.
Still, the problem remains that if your opponent can't play cards because of denial, means that you can't draw more cards than you already have. On the other side, if you can't draw cause he can't play anything, you are probably winning anyway.