Suppress what? To the imperials it is a hard hole to shoot through. They are at range. Hang back where? Out in the open because there wasn't cover? Use what launchers? The mandalorians are going to sit there after the imperials ask "Would you please hold on a minute? We have to run back to the ship and get some launchers to kill you with." And if they could do the last one, the mandos never would have made it out.
And you're still forgetting the armed and free Din that was out there. They wouldn't have had time to capture him had she cut a hole.