On first run through of the new mission (after the patch) and had to use a hireling Rogue to find/locate the hidden door so I could open it to get the 3rd crest needed to advance the mission.
Please make all crests reachable by any character of any level/skill for when they can play it as this is part of the mission.
If a secret door is in a mission and is compulsory it should be locatable (by whatever means DEVS see fit) by all characters regardless of search skill or have a lever to operate it. Failing this go back to writing in dungeon NPCS to join you in quests to help with these normally impassable obstacles for characters not built for those skills.