Depends on your toon. When I first did this it was with warlock using sunsinger. Make sure you take out the knights first, then try and take two wizards out before dealing with mobs. Then go for the last two wizards and mobs. When it came to the crystal, I launched my rockets, however due to mobs, didn't have time to use synth to reload. So in between shooting mobs I ran through the bone like areas left/ right and used super on crystal. Titan striker. Start similar, but as I was using murmur I managed to take out all wizards quickly. After using rockets and dealing with mobs, I found an area towards back left of crystal that has blue lighting. This gives some protection allowing you to deal with mobs, and is close enough for murmur and nades to be effective on crystal.