Sadly most of the Ultima HM wipes I had to put up with where because that last phase Tethered Spheres. I went through so many wipes because players could never move properly for them. Once I finally went in there with a reliable player the tank, myself and that another player did that last phase on our own and it was a sure kill afterwards but it did take a couple attempts to get used to the Tethered Spheres we were tackling due to the allotted time you are given to tackle those last spheres.
