Yes, Another SoF topic (but constructive!)

[Kemiko]

My experience is that pugs usually listen when someone takes the lead. Having the actual initiative to sort things out seems to be out of the comfort zone of your average FF Joe, but people usually follow directions when you explain how and why they should do something.

This right here.
I try my best to be friendly to new players and as the owner of my FC I generally take it upon myself to assist players with content they haven't yet experienced without the need to watch a video. I merely take the time to explain the fight mechanics to everyone in the party and then, if needed, explain and assign roles to those I feel is best suited.
Generally, as far as SoF goes, I assign both myself and a Dragoon to the cannons due to both of those jobs (myself being a WAR) being able to eat the cannon explosion and recover from in it in the form of Second Wind and Bloodbath (both of which recovers by the time the next cannon is destroyed) allowing for more cannonfire before having to abandon it to the next.
I usually assign the Ninja in the party to Dragonkiller duty as they have boosted movement speed and also assign them to Limit Break duty the moment that it reaches 3 bars as sometimes, we can get in an extra bar.
Both I, and whoever else is on the cannons, handles the snares while everyone else just beats up Visharp and, potentially, the adds as well depending on party makeup.
I explain to the other tank to avoid the feet, collect the adds and attempt to remain between the two front legs so that adds will collect in Visharps attackable frames, enabling a clean shot for all enemies by cannonfire. I also explain that some of the adds do have preset targeting mechanics and that all they need to do is Shield Lob or Tomahawk them once and after the add performs its one attack (which isn't anything to worry about) it'll then following enmity as normal.
I then take the time to explain the singular horde enemies, such as the Armoured Dragon, and what to look out for.
Doing these things almost always (not always because I have failed a few PUG runs in Trial Roulette even doing all this) helps to collect a clear. Someone just has to be willing to not assume that everyone will know the fight or that everyone will wipe the fight and waste your time.