Shade of Aran (patch 2.4.3)

Do not stand close to Aran (about 10 yards) because he will casts counterspell frequently, which stops you from casting any spells for about 8 seconds. 8 seconds of not healing isn't exactly great.

Use earth shock rank 1 here to help interrupt the boss' spellcasts. He will use fireball, frostbolt, and arcane missiles frequently throughout the entire fight. Most important ones to interrupt are fireball and frostbolt. Your raid needs to do the best they can to keep the boss' mana up by interrupting because when he goes low on mana, he will polymorph the entire raid to drink, and then he will casts pyroblast on the raid which is very painful.

None of his spells can be absorbed by grounding totem!

When the boss casts Flame Wreathe, DON'T MOVE! You will see rings of fire around couple players, and even if you don't have a ring of fire around you, just don't move to make things easier. People tend to panic when they see people move during a Flame Wreathe.

When the boss casts Blizzard, he will casts it on the outer ring of the room. It looks just like the blizzard that any mages casts, except that it spins around the outer ring of the room. You can't outrun it if you just run along the outer ring of the room so you'll eventually have to cut across the other side. Aran will also casts Chain of Ice during the blizzard on a random player, which prevents you from moving, but it is magic dispellable.

When the boss pulls everyone to the middle of the room, he will begin to casts Arcane Explosion that takes him 10 seconds to casts. As soon as you get pulled into the center of the room, make sure you run towards the walls where the bookshelves are because there is no time to waste as he will casts Slow on you. As long as you run as soon as you see that you are pulled to the middle of the room, you have enough time to avoid the arcane explosion. The arcane explosion deals about 10k damage.

When Aran is down to 40% health, he will summon 4 water elementals. Best thing you can do is use Earth Elemental to help tank one, and grounding totem works on the water elementals. Also, this is the best time to use bloodlust. There is an aggro table on the water elementals.

Things to remember:

-Help interrupt Aran's fireball and frostbolts with earth shock rank 1 as much as you can

-Aran has no aggro table so put earth shield on a spellcaster

-Do not stand 10 yards within Aran as he will casts counterspell on you when you try to heal within his 10 yards range

-Grounding totem does not work on Aran, but works on water elementals

-Don't move during flame wreathe

-Don't try to outrun blizzard, but run across the room

-Run to the wall as soon as you get pulled into the middle of the room to avoid arcane explosion

-Save bloodlust when Aran hits 40% health as the water elementals that Aran summons can make the fight very difficult