Ok, I can break down faction champions like this, hope everyone follow's along.
the npc's you have to fight will vary slightly, in our first 2 weeks of clearing Faction we had the following -
holy priest, holy paladin, shadow priest, affliction warlock,(unknown) hunter, DK, arms warrior, Enhancement shaman, Resto druid, rogue
I'll go ahead and use this set up to explain since it won't really get much harder than this.
Things you need to know:
-These npc's CAN NOT be tanked. There is no meaningful threat issues, they attack players at random. This event is the equivalent of an arena match against say... 9 2.3k rated players vs 25 1100 rated players.
- ALL forms of CC function as they would in pvp, this includes spell limitations, durations, and to a lesser extent- Diminished returns (further referred to as "DR")
- NPC's CAN be taunted, forcing that NPC to attack you for a short duration, but again, there is no sustainable threat table.
It is all about the CC. making sure any class that can fear has it ready, having rogues always keep kick on cooldown, polymorph, hunter traps, blah blah ALL of it will be used.
Healers first. No exceptions. Holy priest, then resto druid, then paladin. I'll go into detail for each one.
Holy Priest: Functions the same as a player, has Prayer of healing, has renew.... essentially a healbot. most of the dps will be blasting priest down as hard as possible, with rogues kicking, priests dispeling and mages counterspelling. During this phaze AoE fears on the other npc's is vital as they will randomly group on someone and gib them FAST. Also, it is important during this time to keep the Druid banished/feared, as will constantly attempt to heal who is taking the most damage. once the priest is down, move to ---
the resto druid: Has Lifebloom, Regrowth, rejuve, etc, etc. At this point most of your interrupters will start putting pressure on the paladin (not in the form of dps, but in silencing/interrupting heals. casters should be still spamming single/AoE fears to aid in spellblocking. simply do the same thing here as you did for the priest.
Paladin: same as the above two, only now you can relax on the interrupts slightly as he will generally have a wait time between heal casts. atleast one priest (preferrably a shadow priest) needs to be closely focused on the paladin, and be ready to Mass Dispel his bubble (yes.. even the NPC pally bubbles), it is VERY important to dispel this FAST, it removes all buffs/debuffs from him which will significantly hurt those who need ramp up time.
also worth noting that mass dispels will need to be spammed in the beginning of the fight as the shaman will pop bloodlust early on.
I'll leave the healer information up, but the other info was removed... it is mostly unimportant now.
UPDATE: As I have been able to talk with more people who have also completed faction champion, I have reasoned that only 3 classes appear to always be the same:
Rogue: By all accounts so far, Subtlety appears to be the only spec rogues appear with. Shadowstep, cloak of shadows.
Warrior: everyone that I have talked to says the same thing. "Bladestorm". Posit opinion is that Warrior will always be arms.
Warlock: Use of Unstable affliction by most of the people I talked to indicates that the warlock is likely always Affliction.
the only thing I can advise is to treat this like an arena, CC constantly, pick your battles, and remember.... Taunt WILL work but in limited duration.