Alrighty, this place is hard.
I'd say AF requires about the most patience and time out of all the instances to date. It takes a LONG time unless you've got a very good, experienced group. From what I've been seeing many times guilds just take their lowbies (<80s) through there piecemeal. It takes a certain amount of experience to really make the dungeon viable. Sometimes it's even broken up into 2 sections (one group clears the bottom, the other the top). VOIP helps tremendously in here unless you've got an experienced group.
So with that, I shall begin.

AF is pretty much a lvl 75+ Instance and the final group of instance quests you get, alongside the endgame raid instance quests. As such, you CAN make it a part of your leveling grind but more often than not people end up doing it post-80 out of laziness. Many people just grind out those last levels in DMC (death master camps). Personally, I think Atzel's is well worth the time and you can expect over 1/2 a level from it alone, maybe near a whole one in some cases.

Party makeup: I've learned that unless you've got an "uber-tank" you really should have a MT and an OT. Ideally this means a Guardian and a Conqueror or DT. It CAN be done with just 1 tank though, in really good groups. Concurrently, w/o 2 tanks you will need LOTS of healing and some crowd control. As it is I tend to go in there with 2 healers anyways. That leaves 2 slots for DPS of your choice. Alter your strats depending. Obviously with a few Rangers you can get away with some pretty interesting tactics. Likewise with Demo and Necro.

The way this instance works is there are "Advisors" (mini-bosses) that will BUFF King Atzel, who resides on the 2nd floor. Your 1st job is to clear the Fortress of these Advisors before even THINKING of attempting to kill Atzel. And no, you cant skip even ONE of them... I've tried - you will get pwned. So on the 1st level you start working your way through.

The KEY here is having your MT do ranged pulls in the hallways and then pulling those mobs into the open areas where your group can do better damage and keep from getting tagged by pats or mistaken next-room aggro. So when you walk in you stay put and let the MT pull the next large room to the group. When that next large room is clear you then make that your "base." And then the MT pulls the group in the next small corridors to the Base, and so on. You do this until nothing is left. Kill EVERYTHING. And yes, certain mobs DO respawn - so make sure your MT gets you into a nice rhythm.

The pulls themselves sometimes are singletons, which are easy enough to deal with. But MOST of the time are doubles and sometimes triples. These baddies hit HARD and can sometimes 1 or 2-shot your clothies... many have DOTs that kill in 2 ticks. So you've gotta be especially careful with aggro. When you pull doubles make SURE the MT has the 1st mob and the OT concentrates on the 2nd. Have the group damage down the OT's mob 1st, and then move to the MT's mob. You'd do this in opposite of course if you're doing crowd control with your mages or rangers. Leave one mob stunned or rooted and dmg. down the others. (obviously) Alter your strats as usual dependant on group makeup.

The lower level boss Fights are simple enough... BUT, the twists are they all usually have VERY hard-hitting minions they call on to help them (much like Magnus). These minions keep coming the longer the fight goes. So basically, you need your squishies to keep these minions off the tanks... if they get to the tanks you're dead. Kill them 1st while the tanks hold their targets.

Another twist is SOMETIMES mobs will "reset" themselves if you try to pull them too far away from their starting positions. If this happens, move your group into the next room or closer (if able to do-so without dying). Typically this happens with bosses but can also happen with trash mobs.

When you've killed all the lower level bosses you move upstairs to the 2nd lvl. The 1st group of mobs however should be range-pulled DOWNSTAIRS while the group remains below in the main hall. Once you've cleared them, move upstairs. Watch out for pats. There are lots of them. Once you're in the 1st hall upstairs (on the wooden decking) have your MT start pulling the next room to you. Once that's cleared move in SLIGHTLY, but do not engage the boss. Have the MT pull the mobs in the rooms to the sides to you. Reason being, these mobs many times will suddenly pat when you think they're stationary... and at the worst possible time. So just clear em out and dont risk it. It also gives you more room to play with for the boss. Once all this is done, engage the boss...

wash, rinse, repeat.

Bear in mind you should always be killing healers and ranged dps 1st when you encounter them... standard protocol

Also, in some of the side rooms you may find quest scrolls so be mindful to look for them lying on tables, etc.

Another hint; only have the healers release if the group wipes. Too often people will choose the wrong spawn-pad and cause a long wait/walk. Make sure EVERYONE has the "Atzel's Fortress" spawn pad before you even start the instance. Above all, make sure someone stays inside if everyone wipes, to prevent the place from resetting.

Once all this is done and all the bosses are killed. It's time for King Atzel... more on that in another post (if I ever kill him)

p.s.
Killing King Atzel is a "right of passage" for many people in AoC; as it is in King Conan's eyes. It's a difficult instance and a very difficult boss fight. So pat yourself on the back if you complete it... regardless of the phat lootz you may have or havent gotten.