Howling Abyss

First boss
The boss will spawn eggs in the room from time to time, make sure to focus and kill them ASAP before they hatch, to avoid adds. Melee DPS should be wary as the boss has an AOE tail-attack that can make them take a lot of damage. The boss will cast ice patches on the floor, be sure to run away from them. After a few seconds standing in them they "explode", dealing a hefty amount of damage and leaving you frozen for quite a while, fully vulnerable. Finally, from time to time, the boss uses a charge, charging at a random member of the party. Just dodge, and he will resume his normal aggro.

Second boss
The second boss inflicts heavy bleeding with some attacks, pay attention to that. He will often start spinning around and jumping from people to people, there is nothing you can do about that. Healer(s) have to be ready to heal everyone when this happens. He can also start spinning and cast magical bullets away from him, you can easily dodge them if you're far from him. Melees should try to stay away from him when he spins, as there's no use taking unnecessary damage. He will spawn icy adds, DO NOT KILL THEM. Kite them all around the arena, they are very slow. His most powerful move is when he starts spinning into a fire column, and then starts flying before causing a massive explosion. It deals A LOT of damage. You can counter it either with the Auramancy spell "Wings of Protection" or by getting close to an icy add. In a few seconds, they will freeze you, and while frozen you are fully immune to the fire damage. You just have to get in their face, it's an aura that freezes you.

Third boss
Hardest boss of the dungeon. She only deals magical damage, so plate tanks will not be able to tank her as they will take way too much damage. A cloth (or leather) user has to tank her, ideally the person having the highest magical protection. There are 4 puddles in the arena, and from times to times, the boss will flood the arena with water. Waterspouts will emerge from the puddles, MAKE SURE to stand in them and get lifted off the water. Else you will take an insane amount of damage. She will place sort of traps on the floor, you can see the hint. If you stand in them, you will be heavily CCed (silence or stun) and open for a burst. Same goes for her fire traps. The elementals she spawns are quite harmless, so focus on the boss to take her down as fast as possible.

Fourth boss
The boss has an attack that will petrify everyone in the party. Make sure, when he starts casting it (the cast is very long) to grab one of the shields laying around against the walls, to "reflect" the spell to him and petrify him instead. When he gets enraged, make sure to stay away from him, he hurts. Aside from that, an easy boss.

Congratulation, you've made it !