The Five Temples of Orr: Temple of Melandru & Temple of Grenth

Since Temple of Melandru is the most straightforward event (and a very bugged one) I'll post it with Temple of Grenth's strategy

Temple of Melandru

Melandru: Goddess of nature, earth, and growth worshipped by her Orrian's follower on the Cathdral of Verdance, the events leading to the cleansing of her temple is probably the most bugged events in Guild Wars 2

a. Escort Magister Izzmek to the site of the first signal beacon
Magister Izzmek resides on Gavbeorn's landing, and it has to be reclaimed before he can move out (though due to some bugs he won't budge), it's straightforward, just escort him through three beacons and you're set, though sometimes he's bugged and will halt halfway

b. Legendary Fight: Destroy the Risen Priest of Melandru
he's though, but his attacks aren't deadly, the most annoying thing when his HP is depleted he'll turn everyone near him into animals and summon five acolytes to regenerate his health (he's invulnerable to attacks at this state), you must quickly dispatch these acloytes in your animal form to prevent his HP to go out to full
BUG: sometimes he won't turn you into an animal and you can continue to hit him until he's down

c. Defend the Pact interrupter device while it charges to cleanse the temple
Another straightforward mission, just defend the device, it has some HP and can withstand some blows, get ready to kite the Champion Abomination around due to it's stacking frenzy, kill the Champion Risen Spider before it can spawn smaller spiders

After the device is online Lightbringer Surefoot will light up his karma store for you

Note: every now and then the risen will tried to destroy the pact interruptor with the event Defend the Pact interruptor from Risen attacks, it's Risen Priest again combined with Champion Spiders, Abominations, and Gorillas

Temple of Grenth

Grenth the God of Ice and Death, his temple is the Cathedral of Silence on an island in the southwest corner of Cursed Shore, and it's cleansing event is the most engaging event ever. first and foremost you must escort the pact from the northernmost tip of the island until it reaches the first event below

a. Protect Tactician Footi as she sets up her cannon
Simple, straightforward mission

b. See Keeper Jonez Deadrun safely to Death's Gaze Torch

c. Ensure that Keeper Jonez Deadrun reaches the Cathedral of Silence
This is where the fun begins, Jonez has a small amount of HP and by the number of people joining the event it can scale up into where the mobs can one hit Jonez, keep them away from him at all costs, especially those bow guardian that can inflict confused condition

d. Legendary Fight: Protect Keeper Jonez Deadrun and destroy the Champion Risen Priest of Grenth
Welcome to hell! there's a LOT of things that you have to remember and DO at this fight

1. Champion Risen Priest of Grenth will one shot Jonez most of the time so keep him at the back of all cost, far away from Jonez, his attack are deadly, it'll spawn AOE brown whirlpools that will throw player up to the air where they'll receive falling damage (on slow connection it'll inflict MULTIPLE falling damage and you'll be defeated instantly), another is spawning ice fields that WILL kill you and inflict chill if you're somehow survived, this is the main problem, dying on this fight is dangerous and annoying since it'll push your ressurrectors to the limit while evading those attacks

2. Shades is your number two number one problem, it has much HP but it didn't do much damage but again it'll give you a stacking corruption when they hit you, after you gain 25 of it you'll be downed instantly. The Shades cant be damaged through a normal means though, there are two brown whirlpools on the left and right corner of the room you must step on it to gain "Entered Grenth Realm" debuff which will give you deathshroud-like appearance, now you can damage the shades but be careful they will inflict more damage to you and stack more corruption when you're in this form, also the brown whirlpool can be re-entered, effectively removing you from the "Entered" debuff which can be annoying when you're shooting shades from afar, since it can't be re-entered again immediately, when you're down you're losing the corruption stacks and the entered debuff. in the past patch you can't ress someone in this state, now you can, thank you Anet, although no thanks for you for giving us endless waves of shades, yes endless, they won't stop spawning although the last wave has not been dispatched, giving you a black nightmare

3. Mobs: there can be hundreds of them, spawning around Grenth's Priest and on the corner of the room, spectral, shades, risen, everything, be sure to get rid of them before they fill your screen (literally)

4. There's no waypoint near this area, the nearest is Anchorage Waypoint which sometimes contested due to bug or assault to Arah, so when you're defeated don't wait for ress because it'll be a long walk for you 

e. Cover Keeper Jonez Deadrun as he performs the cleansing ritual
No, all the chaos hasn't over yet, now come the finale, ress everyone, take any buffs, since hundreds of mobs will spawn from every corner of the temple and tried to take out Jonez, kill them, kill them immediately, sometimes they'll spawn RIGHT IN THE MIDDLE OF HIM which will give you a headache, just interrupt them, launch, knocdown, or whatever your arsenal can do, watch for Champion Risen Spiders and Wraiths that can summons reinforcement, well actually the true enemy in this fight is the lag and the culling which can hinder your performance on this fight

Note: If Jonez defeated on any event he'll come back to his tent on Death's Gaze Touch and sleep for approximately 15 minutes before the event restarted from point a. again

Congratulations! wipe your sweat while enjoying Karma items from Jonez, it's practically the same with the other temples but since you've beaten the most difficult of them you deserved an achievement, there's one? No, let's petition Anet for one =))