There is no bosses in Hyjal Summit instance

** Update** 

Everything is working in hyjal Summit. you need to speak to thrall And the horde camp and Lady Jaina at the alliance camp, as the mobs and bosses attack their camps.. so heres what happens

Alliance Camp- Speak to lady Jaina for the first time, there is a wave of 8/8 that you must complete, After you completed the 8 waves Rage winterchill spawns and attacks the base. After you have done that go back and speak with Lady Jaina Another 8/8 waves to be completed will show up. kill the 8 waves and then Anetheron will Attack. once done that go back to Lady Jaina and say goodbye

Go to Horde camp

Horde Camp- Speak with thrall for the first time he will give you the same lot of 8 waves that must be completed, once the first wave is completed kaz'rogal Will show up, then after he is dead go back to thrall and speak with him he will give you another 8 waves to kill. once that is done Azgalor will spawn. once done that go back to thrall and say goodbye

Run along to the night elf camp, now this camp you don't have to do anything but i think if you speak with the priestest there she will give you a object that will slow fall you. then from there you can run over to attack Achimonde.