Since there already is a guide for the Northrend Beasts, I thought I would put this out here as a Placeholder for Jarraxus. I forgot to take screenshots last night, but will when I run my 2nd group through tonight. The 10 and 25 man versions are identical. Only difference is the amount of damage for abilities, and the health of targets.
Jarruxus is a Doomguard, has above 4mil hps and is an interesting encounter. As I run through the second time tonight I will have a little more details on him.
Basic Group Makeup:
2 Tanks
3 Healers
5 DPS - Preferably 2-3 Ranged.
Jarraxus has some interesting abilities.
Fel Firebolt - Interupt this. Interupt this. If you don't know already, INTERUPT THIS. It does approximately 12-14k on non plate, but then ticks for 3-4k per sec for 5 secs. Not fun.
Fel Inferno - Green fire periodically placed around him. Does damage to everyone within 15 yards. 2-3k per sec. Just move him out of it when he drops it. Not that hard.
Fel Lightning - Green Lightning bolt that jumps up to 5 targets. SPREAD OUT! This is where range comes in handy. Deals 10-12k dmg and cannot be interupted. When you have it, don't run into a group.
Incinerate Flesh - If you have DBM, it will tell you who has it. HEAL HIM IMMEDIATELY. What this does is put an absorb shield on the person for 60k. You have to heal 60k worth of healing to get it to fall off. While the player has it, his damage is reduced by 50%. If it is not taken off before the time expires (15 secs) it will cause a burning inferno that basically 2 shots anyone in its 20 foot radius.
He also summons two things. A portal opens and a Mistress of Pain comes out. She looks like a Succubus. KILL HER IMMEDIATELY. The second is a Volcano that shoots out fireballs on random people that pop into Infernals. Just offtank these and stay away from them.
Infernals - They will occasionally stop and do a short range AOE explosion If caught in it, 14k damage. They don't do a lot of dmg themselves for attacks, so can easily be offtanked.
Mistress of Pain - She hurts. Seriously.
Shivan Slash - A whirling attack that deals 75% weapon damage and pierces through armor. Does about 8k on Plate.
Spinning Pain Spike - Leaps towards a player, grabs them and causes MAJOPR PAIN. Did 12k dmg on Plate. Keep in mind, she can hit you with the Shivan slash and then instantly hit you with this.
Mistress' Kiss - Spell with a short cast time that interrupts a player's current casting and school for 8 sec and causes 5k Shadow damage. Only does this on her current target, so make sure it is a tank on her.
STRATEGY:
MT picks up Jarraxus and all DPS on him initially. Only move Jarraxus when he drops his Fel Inferno and just kite him around a little to ensure everyone can stay out of it. INTERRUPT FEL FIREBOLT every single time. It is a 2 sec cast, so you have time to see it and interrupt.
His first summon will be a portal for Mistress of Pain. OT picks her up and all DPS switches to her. She goes down fast so no worries. Just don't take agro, or you could be one or two shotted.
His 2nd summon is the volcano. Just have OT pick up the adds but DO NOT KILL them. They will die from the tank and incidental dmg, just let them be or their explosion will wipe your raid in conjunction with other abilities.
He alternates Mistress and Infernals. So every time a Mistress pops, switch DPS to her, and leave the infernals alone. OT will need to pickup the Mistress so be ready.
Even if Jarraxus has 600k health left, DPS the Mistress. With the Infernals and her up, the OT will be taking SUBSTANTIAL damage and could get owned quickly. This will wipe your raid.
That's it. I will edit this post with screenshots and other things as I see fit.
Hope you enjoy.