Having a perfectly stacked team and plenty of time, this time trial is literally impossible. crota consistently bugs out during damage phase making it either impossible to deal damage or impossible to finish. He becomes immune or does not kneel or he will just get up before we can get two swings in.
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Try leveling a little bit more. 10 level under is hard for the crota nightmare hunt. Only use heavy attack on crota and do not run into him with 2 people having the sword. Only one by one. If he still gets an attack off, only one dies and the second can deal damage. Its not too hard. I did it last season.