Razorscale is also now absurdly easy. You could probably do this fight with just one person tanking all of the adds and the other one switching to DPS. After the first phase you will need 2 tanks again. We normally run 2 tanks though as our gear hasn't evolved to the point where I trust doing stuff like that. I would definitely not want to go with less than 3 healers until your raid knows how to "STAY OUT OF THE FIRE!"
Composition: 2 Tanks, 2-3 Healers, 5-6 DPS.
The Razorscale encounter consists of 2 phases.
Phase 1 - Dwarves and Chains
Your goal in phase 1 is to hold the little adds off until the Harpoon Guns are repaired. This is astonishingly simple. Adds will generally appear in only 1 area at a time, and should be reasonbly easy to be picked up by a tank. The tank will then drag the adds back to the raid to be killed.
The reason you do this is most of the blue "Flame Puddles" will appear inside the big inscribed circle on the ground. This way you simply avoid most or all of them and greatly reduce the stress on your healers. If you have fail tanks that can't move you CAN tank the adds where they spawn, but that's more trouble than it is worth.
Eventually a message will appear stating "Harpoon Gun Ready!". At this point you need to use said gun. Once 2 have been used in 10man, Razorscale will be held down for a short period of time. During this time ALL DPS needs to switch to Razorscale. You will have a total of 3 of these phases to deal ~1.8mil damage. We usually get it done in 2 if we have the Tanks DPSing her as well. Once she is reduced to 50% she will go into phase 2.
Add #1: Guardians: Guardians are just your standard melee add. They have a moderate amount of health and can be AoEd down.
Add #2: Caster: The caster adds will cast a lot of Chain Lightning. You shouldn't have problems with this as long as people stay out of the blue fire. Can be AoEd with Guardians.
Add #3: Sentinel: Sentinels are bigger adds with a lot more health and a whirlwind attack. Melee will typically want to stay away from these and let the ranged DPS kill them.
Phase 2 - On the Ground
Once on the ground Razorscale essentially becomes a tank and spank. Make sure you burn down any remaining adds quickly before switching to Razorscale. Razorscale will put a stacking debuff on current tank that reduces armor and move speed by 20% per application. For this reason you need 2 tanks to prevent them from getting 5 stacks and being 1 shotted by a breath. All you need to do is just swap tanks and move out of the "Flame Puddles" and then collect your loots!
Note that Razorscale has no Tail Swipe, Fear, or Cleave.
Fireball - Hits a person for ~8000 unmitigated fire damage. Hits one person every 2-3 seconds during Phase 1.
Blue Fire - Spits a blue fireball at a person. Does no damage on impact but does ~6000 fire damage / second to whoever is in it once it hits the ground. These are very easy to see and there is no reason they can't be avoided. Happens during Phase 1.
Flame Breath - Breathes fire that destroys Harpoon Guns. Only happens during Phase 1 after she breaks free.
Wing Buffet - Knocks back anyone around her when she breaks free of chains. Phase 1 only.
Flame Buffet - Increases fire damage taken, stacks multiple times. Raid wide during Phase 2.
Flame Breath - Breathes for ~15000 in a cone and leaves the aforementioned Blue Puddle on the ground. Phase 2 only.
Melt Armor (or something) - Reduces Armor and Movement Speed of her main aggro target by 20%. Stacks 5 times. Lasts for ~20 seconds. Phase 2 only.