Basically:
-divide raid into groups that have a shaman for tremor totem, and any other groups try to make sure they are all undead, everyone should have the pvp trinket.
- go for either a north/south/east/west 4 point split or a semi circle with Archi pushed against the cliff.
-each group must be totally self sustaining, make sure each group has a dispeller + healer.
-give dispellers areas to look after rather than groups, so for example give a mage 'south' and have him dispell anyone that comes into that area, if you try to do it by groups peopel will get thrown out of range and die.
-make sure you do some Tears practice before the boss, make sure everyone has it keybound, and just shout at them untill they do.
-3 things can kill you here, everything else is trivial. The curse will kill people if dispelling is bad or they get thrown far away with it. The fire will kill in the obvious way. The knockback will kill idiots but apart from that forget it, its easy.
-basically the fight is all about individual effort, if 25 people arent on the ball and ready to move away from fire just call the raid off or swap that person out, its very hard to do this while carrying dead weight. Melee should have no problem with the fire, if your melee (rogues+warriors) are gettign fire regularly, shout at them untill they dont. Theres no excuse for a rogue or warrior to die tbh, rogues can cloak, warriors can break fear to avoid the fires.
Right here we go. Tank runs in ahead of everyone else, HoT'd + earthshield etc, in the first 10 seconds everyone should get in position. 2-3 healers are enough on the MT if your healers arent carp. Just dps untill 10 seconds till the next fear, when its 10 seconds away tell everyone apart from the MT healers to run away, it doesnt matter where just get them away from any fire. The fear lasts 4 seconds i seem to remember, they need to be 5 seconds worth of running time away from any fire in any direction, make sure everyone knows how far 5 seconds of running is. You might think 10 seconds is too long and you arent doign enough dps, it doesnt matter, at this stage you need to learn how to not die, not how to kill the boss.
As the raid leader you need to be completely on the ball and looking constantly at the raid so you can shout at specific people who always get fire, its possible to get zero fires all fight, believe me, i managed it for months, shout at people who cant. Once your raid has mastered the fire the rest is just down to making sure people dont die from the curse and fallign damage, the boss damage is rubbish and if the tank is dying you have bigger problems than Archimonde...
Make sure everyone has the ability to see the curse and fire debuffs on their raid frames, especially healers. Force people to get into the habit of using all three types of healthstone, its a must for this fight, as are healing potions, mana pots wont be needed trust me.
try and bring as much ranged dps as possible, 8-10 healers on your first kill.
???????
Profit.
I hope that helped.
Edit: Oh and just to shut up any of the idiots you may have in your raid, THE FIRES ARE COMPLETELY RANDOM. This has been proven btw.