Water can work it's way thru the brick and that is why they put weep holes in the bottom and flashing over doors and windows but it dosn't look like your brick is subject to alot of water. I would spend some time looking for another source for the water. Windows and doors above that door, plumbing leak in that wall or even a roof leak. With a good vapour bairrier on the inside water can travel great distinces before it shows up. If it is a problem with the brick, I would cover the brick above the deck.
I would remove the treated board next to the house and put a 3x3" gavelnized flashing against the brick and replace the board and have a flashing made to go behind the bottom of the vinyl and the house wrap. That would solve any leaking in the vinyl and protect the brick above the deck.
Doors and windows above would be my first guess.