What's interesting to me is that while the game asked for a Caller and a Mapper, for the entire time I've been playing the two player-side roles that always have to be filled are Mapper and Treasurer.
Never had a Treasurer because the party would just split all loot as they found it depending on who could handle the encumbrance.
That wouldn't fly here for two reasons:
--- depending on who the Caller was, the Call might be made before anyone else had had a chance to say anything. Cue arguments.
If a Caller made a unilateral Call, I’d check with everyone to make sure they agree before acting on it. Then remind the Caller that their job is to poll the group, not make decisions.
--- depending who the other players were, the Call would be immediately over-ridden by characters doing their own thing and not going along with what the party had just decided. As in:
Party's at an intersection. Down one passage is a dim green light. Down another is an obviously-important door. Down the third is a low constant rumble coming from the darkness. Party decide to go toward the light but it's not a unanimous decision between the seven players...
Caller: "We're going left, toward the dim green light, usual marching order."
Player 2: "Not me - while they go that way, I'm going to check out that door! There's gotta be some great loot behind that thing!"
Player 3: "And I'm going to go 20' down the right passage, to try and get an idea of what's causing that rumble."
Player 4: "Sigh. OK, I'm staying put at the intersection so I can keep an eye on everyone."
Chaotic parties - and players - for the win!
I don’t see any of this as incongruent with a Caller. Having a Caller doesn’t mean the party acts in lockstep. What would happen is:
Caller: “Me, Player 5, Player 6, and Player 7 are going left, toward the dim green light, in that marching order. Player 2 is going to check out that door. Player 3 is going to go 20' down the right passage, to try and get an idea of what's causing that rumble. Player 4 is staying put at the intersection so she can keep an eye on everyone.”
When the party is chaotic, you Call the chaos! If the party split like that, I would then treat the lone players as their own Caller, or depending on the situation split the party into two groups, each with their own Caller.
The idea is to avoid this kind of thing:
DM: “Down the left passage is a dim green light. Straight ahead is a finely carved door. Down the right passage is a low constant rumble coming from the darkness.”
Player 1: “Left? Left sound good?”
(Muted agreement and noncommittal shrugs from rest of group.)
DM: “Okay, you travel 30 feet and come to—”
Player 2: "Wait, not me - while they go that way, I'm going to check out that door! There's gotta be some great loot behind that thing!"
DM: “Uh, okay. Are you listening to the door or checking for traps?”
Player 3: "If he’s doing that, I'm going to go 20' down the right passage, to try and get an idea of what's causing that rumble."
DM: “Right, okay.” (Thinking:
That’s gonna trigger an encounter. Crap, which to handle first…?)
Player 4: "OK, I'm staying put at the intersection so I can keep an eye on everyone."
DM (starting to scribble on scratch paper): “So who’s doing what now?”