NOTE THIS IS NOT MY GUIDE!
I found this on the WoW forums and used it to get the achivement thought it would be helpful so i posted it here. Link is at bottom to see the OP
The Group
Tank - Prot Paladin
This is the clear choice in our opinion for several reasons: superior threat generation, long-range taunt abilities (40 yards on Righteous Defense, 30 on Hand of Reckoning), performance-enhancing buffs on long durations, ability to make party members invulnerable to physical damage, a 6% healing buff to the party, and the list just goes on and on. Warriors and druids may have a more difficult time with the adds, while Death Knights may be at a significant disadvantage in physical mitigation.
Primary DPS - Fury Warrior
Our DPS warrior (Garim) is duel-wielding Betrayers of Humanity and, for the most part, has the best equipment that we've been able to outfit him with so far (poor drops from raids have been a factor to him not having every BIS). These stats allow him to chew through most players, even those with high resilience numbers.
Secondary DPS - Shadow Priest
A shadow priest provides much needed Replenishment for the healer, as well as the tank (which is arguably not necessary with Blessing of Sanctuary). Another secondary function of the shadow priest is Mind Flaying single targets that attempt to come into the room in which you tank King Varian Wrynn, and using Mind Sear to take out groups of players that come into the room while the fury warrior finishes them off.
Healer - Resto Shaman
A case could be made for holy paladin due to Beacon of Light, but this has to be refreshed every minute, and frankly its much easier to just cast Chain Heal. A second blessing on each party member might be beneficial, but totems (generally speaking) outweigh the value of that. Fire and Earth elemental totems are also a nice benefit for fending off Alliance players as well. Bloodlust helps to push the King down quickly if you're becoming overwhelmed and realize you can't hold off all the opposition.
The Pull
Ideally, you'll want to pull King Varian Wrynn into the Northwest room of Stormwind Keep. This serves several important purposes, primarily, it gives your prot paladin time to lay down AOE abilities while guards are running in, thereby snap-aggroing most (or all) mobs to him while he's tanking the king. Another advantage is that less observant Alliance players may not figure out what has happened to their king, as happened several times for us when we angled our cameras around and noticed that players were running into the throne room and spinning around trying to figure out where he had gone. Obviously, smarter players won't be fooled by this.
The Fight
King Varian Wrynn has a whirlwind and Heroic Leap, with whirlwind appearing to be on a lower cooldown than the Heroic Leap. We discovered that the tank is most in danger of dying because generally speaking he'll target the healer (as he did with us), thereby giving Alliance opposition a window of opportunity to take out your tank and end your fight. I saved Divine Protection and Lay on Hands as well as trinket cooldowns, and potions for this eventuality. The biggest challenge is fighting off the Alliance while still doing respectable damage to the king in order to not draw the fight out to such a length that it becomes impossible to achieve victory as more Alliance join in.
The Timing
Although we didn't know it at the time (since, at the time, we were actually going to Stormwind City to acquire our Coins of Ancestry from Hammershout the Elder), Wintergrasp had started a few minutes after we engaged, which probably occupied most of the level 80 Alliance players at the time.
I hope you find this guide useful... our next target is King Magni Bronzebeard, and we hope we can provide you all with a good strategy for killing him with 4 players.
World of Warcraft - English (NA) Forums -> 4 Manning a City Boss - A Guide
Thank you for reading