ok me and my guild have spent a lot of time trying to get this one cracked and i have found a way to make this work with GREAT ease. first of NEVER take henchmen as the ydo not have infused armour and will die at the first site of mursatt.
im not going to go into great detail of what skills to bring you figure them out for what ever you like.
you will need 2 monks 2 elemens 1 battry necro 2 warriors and 1 ranger, if you cant get a battry just take another ranger.
first off like a post above stated some ppl like to camp the stairs near the king but i have tried this a few times and have always failed

they way i do this is put your 2 eles on the top with the cats ALSO firing them off to kill anything before they get close, if they get in close they can nuke from ontop.
have 1 monk on each gate and your ranger on the west gate setting as many traps as possible. along with a warrior to help out.
the key to this way is communicat to each other... what every gate you are on let the others know if its clear or if you have incomming.
if you got incs yell and have the other warrior come over the help leaving the ele as your look out on top incase some come from the other side if they do get a warrior and monk to run back to hold them of as you mop up the ones on the other side.
remember the key is ALWAYS have the eles firing the cats non stop and good coms with each other.... this is by far the best way to do this and since i have figured it out i have not failed to do it once even tho i have lost 1 monk and 1 warrior we still managed to do it.
good luck