Fat chance that the Red Proto-Drake will be gone any time soon since it's only a 280% flight speed mount. Still, anyone after the Red or Blue Dragonhawk mount (when Blizzard gets off their backsides and increases its speed to 310% instead of a measly 280%) from Mountain O' Mounts should count the Red Proto-Drake among the 100 that they'll need. Or you can just look a lot cooler riding on a big red proto-drake instead of a puny red or blue bird that looks like it would snap in half if a Tauren sat on it.
The achievements from the heroic five-man dungeons aren't as difficult as they used to be pre-Ulduar, but a lot of them are still a pain in the backside. They're all listed here per dungeon, all rated for their difficulty with the appropriate tactics and under the assumption that the groups trying for this are decked out in Naxx 25, Ulduar 10/25, or ToC 10/25 gear.
On The Rocks
Defeat Prince Keleseth on Heroic difficulty without shattering any Frost Tombs.
Don't use AoE attacks, period. Any tank can take Prince Keleseth without relying on their AoE skills. Frost Tomb is an indiscriminate spell, so the tank, DPS or healer could be a victim. Take multipurpose classes if you're paranoid.
Defeat Grand Magus Telestra on Heroic difficulty after killing her images within five seconds of each other.
Simply using AoE attacks would do on Telestra's images, but groups with fewer AoE attacks would do well with controlling the amount of damage done to their targets. 40% for each image would do if there are DoTs on each. Keep an interrupt-capable class on the Frost image to cancel her channeling or else she'll refuse to die until her Blizzard's channeling time has finished.
Though she should split twice for the fight, killing her before the second split still grants the achievement.
Defeat Anomalus on Heroic difficulty without destroying any Chaotic Rifts.
Clear out all of Anomalus' rooms before you start this achievement. Your team will need several choke points to AoE the adds that spawn from the Chaotic Rifts without accidentally destroying any Chaotic Rifts. Your healer should be ready to heal everyone because of the massive arcane volleys from the adds until Anomalus stops channeling energy.
You'll need at least two choke points. The first choke point is the first ramp leading to Anomalus and the second is next to the ramp leading to the bridges that go to the south exit of the room. If these aren't enough, work your way to the south exit and beyond until Anomalus goes down.
Defeat Keristrasza on Heroic difficulty without allowing Intense Cold to reach more than two stacks.
Equip your insignias and ready any of your root-removing spells to be safe. Once the fight starts, jump, strafe and squirm your way around the room to keep Intense Cold from stacking on you. If she roots you, use whatever you have handy to free yourself.
Even with the best gear, Keri will hit you with at least one Frost Nova.
Watch Him Die
Defeat Krik'thir the Gatewatcher on Heroic difficulty while Watcher Gashra, Watcher Narji and Watcher Silthik are still alive.
If your group's gear is good enough, you can DPS your way through this without caring about the little details.
Groups with lesser gear beware: two of the three Watchers are nasty. One will poison the entire party and the other will disorient the entire party. Both have interruptible casts, but a Shaman is preferred for their Poison Cleansing totem while Insignias can deal with the disorientation.
If you're taking it slowly, start the fight by killing the Skirmishers. They reset their threat tables frequently and hit hard and then turn your attention to the Webspinners.
And all throughout, keep everyone out of the web wrapping.
Defeat Hadronox on Heroic difficulty before he webs the top doors and prevents more enemies from spawning.
Cheat your way through this with ease. Take any class that can drop their threat table and have them engage the mobs on the web. After they lose their threat table, the mobs will despawn. Everyone should then run down the web to Hadronox's lair just before the hole in the web. You have 30-45 seconds after Hadronox spawns to kill him. Don't let the Hadronox's poison kill anything or he'll heal.
Defeat Anub'arak on Heroic difficulty in 4 minutes or less.
It's a DPS race. Hit him until he burrows, then kill the mobs until Anub'arak comes back asking for more punishment. The time limit is incredibly generous.
Ahn'kahet: The Old Kingdom
Respect Your Elders
Defeat Elder Nadox on Heroic difficulty without killing any Ahn'kahar Guardians.
Take an off-tank with you and a second healer or have the off-tank survive long enough to nuke the boss.
Clear the area beyond Elder Nadox, particularly the balcony overlooking Prince Taldaram. Once you're fighting Nadox, take him to that balcony. Your off-tank should stay inside Elder Nadox's room and pull any Ahn'kahar Guardians before they go through the doorway and give Nadox immunity.
The Party's Over
Defeat Prince Taldaram on Heroic difficulty with fewer than five people.
Okay, so bring four people and beat the bloodsucker into the ground. You'll need to deal 40,000 damage to stop Embrace of the Vampyr before the victim is drained dry.
Defeat Jedoga Shadowseeker on Heroic difficulty without killing any Twilight Volunteers.
Jedoga gains a huge damage boost when one of the Twilight Volunteers is sacrificed. Melee DPS can be killed in one hit from a powered-up Cyclone Strike, so anyone in melee except the tank should beat feet until her enrage ends.
Volazj's Quick Demise
Defeat Herald Volazj on Heroic Difficulty in two minutes or less.
Doing this requires that all of your DPS be competent enough to kill the illusions during Insanity. If each of your DPS can kill their illusions within 20 seconds or less during both phases, you're golden. Just watch out for the Priest healer and its powerful Greater Heal.