Mission Changes:
This is mainly a way to try and deal with some PUG issues that crop over and over again (People not working together, not focusing on the same target, not bringing interrupts, etc.) The idea is to put in early on missions situations where people will have to (focus fire, interrupt, etc.) to win, along with someone pointing out the required tactics, in situations where the party won't get killed,just slowed down a ton, to get players used to doing stuff like this. I'm not actually sure how these things would work for most problem players, but some would likely be helped out by these changes.
In Prophecies:
Fort Ranik: There would be a couple groups of 2-3 Charr casters near a "charr healing circle". Before fighting them, some ascalon soldiers say something like "There are some charr healing circles. We will all need to attack one charr to overcome the healing powers", if too long passes after the fight starts, the ascalon soldiers will say something like "I will direct the attacks, follow me", and in team chat will call the targets. The idea of this is that instead of the mission failing, it just goes on and on unless people figure out to focus fire, and/or read team chat and follow pulls (Or until people start leaving, which is something I'm not sure how to deal with in mission structure.)
Ruins of Surmia: Something similar would occur, only with Rurik directing. 2 healing circles would appear.
Nolani Academy: A similar Healing circle would appear in the middle of the city.
Borlis Pass: A large group of Dolyaks could keep the focus fire importance going in the early game, so a few would likely be added in the mission path. Also, Interrupts start to appear for several classes at this point, so having some stone summit groups with long cast time, dangerous spells, plus a friendly dwarf saying "We need to stop those guys casting, use yer interrupts", or something to that effect, would provide a way to include that sort of stuff in the mission.
Frost Gate: The same sort of stuff as Borlis Pass could be added in here.
Gates of Kryta, D'alessio Seaboard, Divinity Coast: Pulling might be added here, or a threat system, along with some additional strong healing groups and groups to be interrupted.
Jungle Missions: The jungle missions seem to have a lot of stretches where people just run along killing stuff, so interrupt requirements, focus fire groups, etc. would be worked in to those stretches, probably using healing plants and possibly shining blade people and white mantle pointing it out and calling targets occasionally.
Riverside Provice/Sanctum Cay: At this point is where the early game pointing out of how to work as a team should star to pay off, these missions requires some tricks and coordination to get through.
Factions:
Minister Cho's estate: This had a bunch of tutorial elements dealing with things like focus fire, calling targets, and related abilities, so probably wouldn't be changed much. The big change would probably be suggesting that people bring along utility skills like interrupts, damage reduction, and such, which come in handy in the last fight.
Zen Dajun: Some of the "groups of people needing focus fire, needing interrupts, etc", would be added to this mission, as well as the boss at the end, along with Togo continuing to point this stuff out. The bosses at the end are also pretty challenging, so pointing out the skills needed should help in showing people how to fight this sort of stuff
Seitung Harbor to Kaineng city: This was a big jump for a lot of people, so some extra primary quests would probably be added. First, the character would have to go up to Kaineng city, which has the next armor upgrade, and talk with some official of the emperor. Than, the character would be sent through smaller groups of Am Fah, with some sort of scout or spy to take them through less dangerous areas, than they would go to Vizunah Square by the normal routes.
Vizunah Square: The missions hit full level 20 ones here, so only the beginning of Vizunah square would continue on the "how to work in a group" tutorials, against the Am Fah, Jade Brotherhood, and small groups of afflicted. There would only be one big fight in the square, probably in the middle of the mission, instead of the three already in.
Nightfall:
Chabekh Village: This wouldn't be changed much, it already is pretty much a turorial mission, with a small amount of skills involved.
Jokanur diggings: Kormir and the traps are perfect for adding in healing groups, monsters where interrupts are needed, and more called targets.
Blacktide Den: The pirates/Kourna Soldiers would probably serve in the roles of "person who points out stuff like focus fire", and groups of bog creatures would be added that would work as the necessary long stuff to kill.
Consulate Docks: This is where a lot of "how to work as a team" stuff could easily get introduced. Kormir is running with the group, and could point this sort of stuff out, and the various Kournana bosses all provide different challenges that would show the types of utility skills needed to fight different types of tough enemies.