it can't be helped. the guides actually can be summarized into 3 types from what I can tell:
1) gank boss early and slow shadows and kill boss before shadows escape (the video I just linked)
2) block shadows early and only release them when you start fighting the boss (key kii)
3) block shadows and duel boss at the end, splitting into 2 teams. this method relies heavily on multiple healers and rather good tanks (poor troopers)