Does atk spd do anything for him?

I saw somewhere that Hell's Lament was the best option. Any info available on that?

Why is DPS gear recommended? Doesn't he need healer gear?

I think I remember watching it but I don't remember the conclusion. That's why I was surprised Hells Lament isn't listed as recommended at all.

What's the comparison between infernal roar and Hells Lament?