What are the essential differences you need to know about when going from 10 to 25 man Ulduar? Here are the changes. This does not explain hard modes, and therefore also excludes Algalon.
I assume you have watched TankSpot videos and read strategy guides, so this does not cover those basics of positioning and phases.
In the 25-man column I’ll describe if the ability or your strategy needs to change. If something simply hits harder, I’ll still say ‘no change’. Bosses do more damage and have more HP, which I don’t list either.
Healers need to play differently, too. Paladins for example can’t spam flash of light, it’s just not enough HPS. Your tank will be taking so much more damage and you’ll also have more damaged raid members per healer than before, you must have assignments to ensure everyone has appropriate coverage.
DPS: the bosses have up to 5x more HP than in 10-man, but you only have 3x as many DPSers in the raid. You are more likely to come up against enrage timers.
We also have a guide written specifically for off-tanks in Ulduar and Coliseum, that you can read as a supplement.
|Raid composition||2 tanks, 3 healers, 5 dps||3 tanks, 6 healers, 16 dps
Some fights are easier with 4 tanks and 7 healers
Outdoor bosses: Siege of Ulduar
|Vehicle set-up||2 Siege Drivers
2 Siege Gunners
2 Demolisher drivers
2 Demolisher Gunners
2 Chopper drivers
|4 Siege Drivers
4 Siege Gunners
5 Demolisher drivers
8 Demolisher gunners
4 Chopper drivers
More info wowwiki
|Tank setup||Two tanks||No change|
|Gravity bomb||You cause 12 yard AOE
|Light bomb||You cause 10 yard AOE damage||No change|
|Tympanic tantrum||All receive AOE damage||No change|
|Summoned robots||You should: AOE kill scrapbots, off-tank pummelers, kill boombots.
Position XT002 near a pile of rubble to reduce how many spawns you get.
More info wowwiki
Keep reading for the differences between 10 and 25-man Ulduar bosses.
|Tank setup||Two tanks||Two works, three can make Constructs easier to pick up|
|Positioning||Casters and healers up on a wall makes the constructs easier||Same|
|Activate Construct||Every 40 seconds, will usually go straight to a healer.
Tank can stand in plume and eat the 3700 dps they’ll take from fire
|Every 30 seconds
You can crowd control the Construct to keep him in plume
|Flame Jets||Casts fire up through the ground, 2.7 second cast time, interrupts casting for 8 seconds. Stop healing before it happens||No change|
|Slag Pot||Random one person gets 3.5K dps, needs assigned healer||5K dps|
|Strength of the Creator||Ignis does 20% more damage to MT whilst a Construct is alive||No change|
|Scorch||Creates the fire plume you put Constructs into. Frontal attack. Tank repositions Ignis after this||No change|
More info wowwiki
|Tank setup||Two tanks||Three tanks|
|Iron dwarf spawns||Pick them up, separate big guy (Sentinel), burn little guy (Watcher)||Sentinel’s whirlwind can one-shot non-tanks, so separation crucial. Third tank is so you can pick up all adds; third can just waits for Sentinels then peels them off.|
|Harpoon||Three shots to bring Razorscale down||Four harpoons|
|Devouring flame||Targetted at a raider in phase 1, and only at tank in phase 2, leaves AOE blue fire on the ground||Hurts more|
|Fuse armour||The debuff slows the tank and reduces armour. Taunt at two stacks. Last 20 seconds||No change, but your third tank can be handy here as a fallback|
Corridor bosses: Antechamber
|Tank setup||Two tanks: one for torso, one for trash||Three tanks: one for torso, one to taunt from him when Crunched, and one for rubble.
Optionally a fourth as backup in case torso tank get Gripped
|Crunch armour debuff (caused by Overhead Smash)||Minus 25% armour to tank. Nerfed so it does not stack; no need for offtank to taunt||Can stack. Off-tank needs to take over at 2 stacks.|
|Focused eyebeam||Single-target damage, with AOE to those in 3 yards||No change|
|Shockwave (from left arm)||All receive AOE damage||No change|
|Stone grip (from right arm)||One member squished, needs healing or will die, attack right arm to free them||Three members squished|
|Rubble, earth elementals (spawned by arm death)||Need to be off-tanked, have 10 yard AOE that also debuffs, so kill with ranged. Can be brought near to torso||Their AOE hurts more. Should not be taken to torso.
Tank who has the Rubble’s debuff should not take-over Kologarn until its faded.
Must kill with ranged only
|Petrifying breath and brittle skin||Only caused if you screw up, tank needs to be in melee range||No change|
More info wowwiki
|Tank setup||Two tanks, one for Auriaya, one for spawns||Three tanks, optionally four.|
|The pull||Two sentry cats for off-tanking||Four cats for off-tanking. Keep them slightly apart from each other to minimise their self-buff|
|Horrifying screech||5s AOE fear||No change|
|Sentinel blast||Channelled damage, should be interrupted.||Assign players with both a fear-break and an interrupt, to stop Blast when cast after a Screech|
|Swarming guardians||Lots of mini panthers, AOE them down||No change|
|Feral Defender (spawned)||Pounces. Everyone stacks on top of tank facing boss. Creates void zone on death. Can be stunned just before death to help positioning.||No change|
Keepers of Ulduar
|Tank setup||One tank with Frost Resist gear||Optional second tank with FrR and MT without|
|Biting cold||Stacking debuff, prevented and removed by moving||No change.|
|Freeze||Targetted freeze, freezing your feet in place for 10s. Use mass dispell, hand of freedom, escape artist and so on.||No change|
|Flash freeze||Iceblocks everyone who didn’t get onto a snowdrift, marked by large white circle. NPCs need releasing too.||No change|
|Frozen blows||AOE damage to all, large hits to tank in FrR gear||No change, except can optionally use a single tank in normal gear or an off-tank with FrR taunts.|
|Icicles||Small white circle shows impact zone to get out of||No change|
|Toasty fire, storm power and moonlight||Good buffs. Encounter depends on good use of them. Four NPCs cast them||No change, but eight NPCs are up.|
More info wowwiki
|Gauntlet team||1 tank, 2 dps, 1 healer||1 tank, 6 dps, 1 healer. cc optional if you have trouble|
|Gauntlet mini-bosses||Runic Colossus, has frontal attacks including Smash which the tank should run through to avoid.
Ancient Rune Giant, has immobilising attack that explodes target so all must spread out. Can buff allies.
|Arena team||AOE tank, and remainder of raid||2 or 3 AOE tanks, and remainder of raid|
|Arena itself||Charged orb does Lightning Shock, so move away from the charged edge.
Stormhammer, cast-speed slow to members near the target, so casters need to spread out.
|Arena Dark Rune mobs||Evoker, need their self-buff Runic Shield dispelled. Can heal allies with HOT, dispell it. Priority kill.
Champion, can mortal strike, charge and whirlwind. Kill priority 2.
Warbringers, buff allies but otherwise just meleer.
Commoners, trash mob.
|Champion can be tanked to the side due to whirlwind.
Mind control a warbringer to gain their buff and use during fight.
|Chain lightning||Increases damage per jump, so spread out.||No group should have more than 3 players in it. All players should be at least 5 yards away from players in another group at all times. If it chains to a 4th person, they’ll die.|
|Lightning charge||Charges one pillar in the room, so move away from it whilst still remaining away from others (to avoid any chain lightning). The charge pattern will be in a large cone with Thorim being the tip and the lightning orb being the base. Tanks will move into the safe zones.||You need to know in advance the movement patterns from and to for each team. The wowraid guide has a suggested diagram.|
|Unbalancing strike||Big hit with debuff that reduces tank defence skill. Other tank needs to taunt and take over. Will come 5 seconds after lightning charge.||No change|
|Tank setup||Two, one Auriaya, one on spawns||Three, two for the spawns|
|Elder Stonebark||Has Fists of Stone, 2.5 second cast, other tank needs to taunt from range and kite until it fades.
Has Ground Tremor, 2 second cast, causes 8 second spell interrupt, so casters must stop their spells before it hits
|Elder Ironbranch||Casts Impale on tank, large damage over 5 seconds. Can be healed through if watched-for.
Casts Strengthened Iron Roots on random target, which need to be attacked to be freed. Showing nameplates helps find it.
|Other tank must taunt during Impale|
|Elder Brightleaf||Puts Sun Beams which you must pull him out of. Kite continually. Does randomly variable damage due to Flux buff.||No change|
|Eonar’s Gift||A tree that grows, must be killed. Heals her. Assign ranged to the task and call out when one spawns.||No change|
|Sunbeam||Randomly targetted on player, causes damage to allies within 8 yards; move away from others.||No change|
|Wave: Storm Lasher, Ancient Water Spirit and Snaplasher||Spread out. All must die within 12 seconds of each other.
Storm Lasher (white plant) casts chain lightning, can be stunned and interrupted.
Snaplasher (green plant) gets immobilised after enough damage, but that resets in 4 seconds unless still attached. Will not attack melee target if it has agro on a distant tank.
Ancient Water Spirit, charges, tank facing away from raid.
|Use two tanks on adds
Snaplasher does not immobilise. Let a tank build aggro on it, then slow/cripple/stun it so that the tank can kite it.
|Wave: Detonating Lasher||Wave of 10, explode on death. AOE to 30% then switch to single-target whilst spread out. Reset agro continually.||No change|
|Wave: Ancient Conservator||Large guy, casts silence which is prevented by hiding under mushrooms.
Casts Fury on random target (can be the tank), that damages nearby allies. Move away from others.
|Nature Bomb (cast by Freya in final phase)||She has a visual cast, which spawns 10-15 bombs. Tank can move between two locations as they’re cast and explode. Bombs look like small glowing green earthroot.||No change|
More info wowwiki
|Tank setup||Two plus a ranged tank (shadow priest or warlock)||No change.
Optionally an additional main tank can be a backup in case Plasma kills your first tank
|Proximity mine||9K damage||20K damage, so must be avoided, and tank needs particular awareness
|Plasma blast||17K dps on the tank, requires organised and sequenced use of tanking and priest cooldowns||30K dps incoming, ouch|
|Napalm Shell||Targetted, unavoidable, requires healing on the target, and raid to have been spread out to avoid its AOE||No change|
|Shock blast||15 yard wipe AOE, 5 second cast, you don’t have to move all that far, and you cannot run through the boss to get away from him out the other side (must run away)||No change|
|VX-001 assault canon|
|Heat wave and rapid burst||Damages raid||No change|
|Rocket strike||Kills you. Move. Learn to focus on more than one element of game field||Two rockets|
|Laser barrage (preceded by spinning up)||Kills you. Pre-empt it, move during the spin-up.
Melee step back a little so you don’t cross into its frontal attack
|Aerial Command Unit|
|Drops Bomb, Assault and Trash bots||One tank on all the trash, the second on the bomb bots. DK is good for bomb bots as Death Grip can pull it away from the party. He just waits for them to spawn.
Ranged ‘tank’ on the Unit in the air.
|No change but ‘Magnetic Field’ cast on tank needs to be dispelled|
|Final phase, V-07-TRON|
|Combines his previous skills||No change, just a lot more to watch out for||No change|
More info wowwiki
|Tank setup||One. He hits hard||No change|
|Shadow crash||Targetted projectile, creates beneficial energy field, not cast on melee|
|Searing flames||Must be interrupted, 2 second cast|
|Surge of Darkness||Big increase to his damage output, 3 second cast, should be kited or (only in 3.1) tanked by a DK|
|Mark of the Faceless||Damage on ranged target, heals him. Can be removed by ice-block or pally bubble.
Four raiders outside 15 yard radius prevents it cast on melee
|Nine players outside 15 yards|
whoa he looks complicated. I’m not going to write it up until I’ve seen him myself and can really understand what’s important or not.
Thanks to my tanking mates at dk.info for their input.
If you see any inaccuracies or crucial strategic differences I’ve missed, please comment and let me know. Writing this helped me understand the fights, and I hope it helps you win them too.