I remeber when i had just hit 70 and wanted the relics from the chest, i 4maned(4 elly shammys) the gatekeepers easily. They have maybe gotten some puckback or some other new stuff now with last patch.. but i cant see how you have truble with this.. Just spred them out... move your pally in front to tanking them... And when he rases his hammer you stop nuking and move out of range. Heal up party to full and w8 for him to calm down with the hammering. Then on him again..