1st Have the person who is tanking pull the Cursed Shrew out of the castle ruins when the boss is by the fallen tree have another pt member pull the boss off of the person who is tanking, then the person who now has only the mobs on them will run up in to the corner of the rocks that will make the mobs run back into the ruins. The pt can now focus on the boss.
2nd Hopefully you have at least a lvl 55 divine priest when you go because here it would be wise for the priest to bubble the tank as you run up the ramp and then up the stairs into the corner of the castle (make sure pets are recalled) this makes the mobs loose aggro from the pt and you may now fight Gehn the Bloody Butcher. Once you have him down fight off what mobs are left.
3rd Bubble the tank again and they will run up the stairs and to the LEFT fight off those mobs. Once those mobs are dead Kill the Storm Witch she is random aggo so even if you are the tank anyone may become the target of her fury. Around 25% health left she goes into a furry mode where several mobs attack (usually the healer sorry). When this happens it is best for a player with a strong aoe attack those mobs to gather them off the priest. Once the Storm Witch is dead fight off the last few remaining mobs. VERY IMPORTANT!!!!! after you have defeated the storm witch and once you start the Nudo Stormscale if you die wait until the a healer can rez you, if you revive yourself you will become locked out of the top part of the castle once you go up the ramp and up the stairs the entrance will be closed so wait to be re-zed.
4th Then go up the small set of stairs and squeeze around the building into the area below. Once down there re-pot/buff then someone with a long range attack hit the Nudo Stormscale if done correctly he will be the only boss to come. If not done correctly it will be harder because 2 mini bosses will follow as well (kill the mini bosses first will make this easier if they come to). Once he is dead kill the two mini bosses if you did not previously aggro them.
5th If you have managed to not completely party wipe by now congratulations! If you have not taken longer than 30 min to do all of this you will be able to do the 5th and final boss. Vondalynn Moonlight she spawns tornadoes STAY OUT OF THEM they take 1000 hp per second they are on you. Also this boss has a reflect by skill type. She will call out in normal chat 2 skill types (dark, physical, light, earth, fire, etc.) When she says those skill types do not use those types of skills or you will be hit back. Once she has died there is a curse that is placed on random party members that after a minuet you will die. The best way to get out of this curse is to go to the change character screen wait a minuet and log back into game.