An offense can easily commit 7 guys to pass pro if they want to - 5 OL, a TE, and a back.
When AD is double teamed that leaves 5 guys to block the other 3 DL in a straight 4 man rush. The offense could actually double team 3 guys if they wanted to. And unless the Rams blitz 4 guys everyone is going to have at least one blocker on them.
Even in the rare case where AD is triple teamed that still leaves 4 guys to block the remaining pass rushers. Unless the Rams blitz 2 guys when AD is triple blocked the pass pro can man up on everyone else.
(i.e., typically no one has a free pass to the QB.)
AlbaNY_Ram