and for draven, is a triforce worth it with W spamming? I think I'd rather go for a bloodthirster + the other lifesteal and damage item (with the mana)
No, not in my opinion; and please never build essence reaver on anybody besides maybe Ezreal, or any caster type adc.
The statik shiv is nice on draven with the Q's, but if the enemy team lacks large amounts of heavy cc and lets you stay and constantly basic, critting more often with your Q's > occasionally bursting with it, so phantom dancer would be better. However, if you can only attack safely every now and then, then yeah, usually shiv is more worth.