Can someone answer me some questions about dualwielding flickerstrike raider?

POE-Ninja shows 2 flicker strike raiders with high damage. Those are dualwield raiders. From my perspective there are no mandatory items for this build to run.

My questions:
1. Where does their damage come from? I'd guess it's a mix of critical strike damage and added flat physical damage in combination with their passives and ofc 2 really good foils.
2. Both are using blood lust support in their flicker strike setup, but I cant see any source of bleeding. Is there anything I am missing something or are they played with another character who applies bleeding?
3. Are there really no mandatory items to run this build? What's about all those "reduced mana cost" items? I know the helm adds a lot of damage, but is it really mandatory?