WoW timeline in a nutshell:
Seriously, the whole timelome is fucked. Start in a world, damaged by the Cataclysm. Deathwing must be stopped. Go into capital city, where it is four years since they hung up a corpse piece of Deathwing, in order to get quests to help the places damaged by your biggest threat, the dreaded Deathwing. After you help the world fight Deathwing, go seven years in the past to fight the first crusade against the Burning legion while your faction fights the last crusade of the Burning Legion. The difference is that your faction knows the Illidari, Lady Vashj, and Kargath have good intentions to stop the Burning Legion. Luckily, you will help your faction, by killing Lady Vashj, Kargath, and Illidan. Then, venture to Northrend to kill the threat of the scourge from the Lich King, despite all us knowing that the Lich King is needed after we killed the Lich King. Kill the Lich King and make a new Lich King. Deathwing appears all of a sudden and destroys the world to the state it was you quested in before Northrend and Burning Crusade. Now venture this new old destroyed world and defeat Deathwing.Oh no, a new land appears in the Mists, along with a new race that you've been seeing or playing for about 2/7/9/2 again years ago. The horde warchief, who was Garrosh but then was Thrall but is now Garrosh again who is dead but also is conquering and ruining the already ruined land of the Vale of the Eternal Blossom, which no one has been able to pass the wall for centuries. Garrosh then goes back in time to a new old Outland and starts an army of guys who are dead. This screws up and causes the Legion to attack once again. Guldan, A guy who's dead but not in this timeline goes to the timeline where he was dead and tries to bring the legion to Draenor. You then possibly kill Guldan but he isnt actually dead and he tries to harness Illidan which you thought you killed but is not dead. Also Garrosh is dead and the hordes new warcheif is Voljin who is also dead. Now stop the Legion who is finally stopped but Azeroth is dying because Sargeras, who is dead from Illidan who was dead, then wasn't dead and is now dead, stabbed Azeroth. What will happen next? Follow the horde warcheif Sylvanas (A girl who died, killed herself, died, died again and is running out of deaths to die with) to find out.
Edit: Explaining who Sylvanis is. She's dead.