Stage 6
Often the last Stage for many squads under 80 and some over 80 if they messed up . There nothing special at the beginning. The mobs are tough but easy to kill. After the second wave you will notice suspicious silence. Attention!!! Two waves of mobs are coming at the same time. As you killed the last mobs of the second wave the cleric and DDs should cancel their AoEs and use Dew of God Protection to absorb damage. Although the description says it lasts for 30 seconds it actually lasts about 180 seconds, note that this might be different for pwi. You may also want to use a Healing Orb, increases HP regen by 100 for 10 minutes. When that's done start the AoEs. BM waits until a large group of mobs gather together and takes agro by using AoE skills. A few seconds later Barb steals mobs by using Roar. Don't forget about Tranquilizing orbs, invulnerable for 8 seconds. Six seconds after Barbs mass agro Veno should cast Parasitic Nova. That gives the squad a few more seconds. Then again the BM uses stun skills. The whole squad spams pots, red and purple, non-stop (don't be shy ).
To be successfull, coordination of Veno, BM, and Barb actions is required. Voice chat! Not the text kind. Barb and BM should keep an eye on the cleric and DDs HP to see when to start their stun/agro cycle. Often one of the DDs will die here. There's a risk to be ported to Thousand Streams. Come back to the squad ASAP. Veno should use spark transfer and the DD can use chi pots as well. If you make it past the double wave you're more than half way to victory. If not, don't get upset, keep trying .
Don't relax after the double wave. Fire mobs are incoming. They can finish off your squad if not all of the double wave mobs are dead.
After all that the boss Flame Strength will look like a joke despite the fact that it comes with three Heaven's Judgments. On this boss the cleric should pay close attention to his/her BB. It might be canceled so reset it ASAP. Wizard and archers keep their AoE going. Barb tanks the boss while Veno Herc tanks and kills the Judgements. If there isn't a Veno or the Veno doesn't have Herc the Barb tanks the Judgements too. It takes 5-10 minutes to kill them. When that's done get the reward and rebuff. Leader should raise HP regen and Defense Aura's to max, and if there's enough left raise chi regen.
Stage 7
Take your spots ASAP the mobs in the first wave are fast. One of the waves will bring horsemen again. Use the same tactics as the last group. Veno's, at wood wave, try to use your Parasitic Nova on mobs without magic immunity or stun won't work. This boss - Shattered Soul is easy. The cleric can keep the BB up while the Barb tanks. At this time some items usually require repairs so you can go do it one at a time. This boss takes 7-10 minutes to kill. Rebuff and max all Auras.
Stage 8
The last Stage with normal mobs. The first wave are fast mobs again. You will see more Heaven's Judgements and horsemen. This boss - Broken Mind is easy. The barb tanks. This one is killed even faster than the previous one. Rebuff for the final boss.
Stage 9
The final boss - Element Lord is the second hardest moment in Gods Rebirth after the double wave. It has a huge amount of HP, short range physical AoE (deadly for robes and in some cases light armor builds). How to kill it? Barb and BM stay at the pillar while all others fall back towards the portal. When the boss comes the Barb takes agro. After a few seconds, to make sure the barb has agro, the BM starts his/her attacks. The most important thing is to keep the boss at the pillar. Auras help a lot, though charms will still tick. A bit later the DDs start their attacks. Archers use Sharpened Tooth Arrow taking off large amounts of HP. After the archer takes position at max range the cleric sets bubble at max range to heal the DDs. Wizard and Veno use their normal long ranged attacks to stay inside the BB AoE. Veno uses Herc on the boss. Auras will heal Herc too. If you have a brave light armor veno (not robe!!) in your squad she can Amplify Damage from time to time. Another important thing is for Barb and BM to use Vacuity Powder in rotation to avoid stuns, because this boss stuns very often. If they don't have powders then they should tell the squad when they're stunned so DDs can stop their attacks as they can easily steal agro and die. If it happens the barb should get the boss and take it back to the pillar ASAP when stun wears off. After stun is off DDs can resume their attacks. Note for DDs: remember that if you die you'll come back without Barbs HP buff so your chances of dieing again grow. Attack carefully so you don't steal agro and mess up all the squads work. Use damage absorbing meds if needed. At 50% HP it will be really had to take agro from the Barb so you can increase your DPS.

Thank you for you attention!