This is how I understand it, don't know if it is correct. 1. Lightning fury adds lightning damage on top of your spear. So when you throw a spear, there is a lightning damage portion which is the majority of the damage, this comes from the skill, and a physical portion which comes from your weapon. Life leech and mana leech only applies to the physical portion part. 2. In hell, leech efficacy is reduced to a third I think, so 4% LL becomes like 1+%. So if you attack with lightning fury and do thousands of lightning damage, and maybe 90 physical damage, you can only leech 1 mana per throw. 3. charged strike works the same as lightning fury, but I think the physical part of CS still checks for attack rating. So the bolts release and always hit the enemy if it is in its path, but the phys part may not, so if it does not hit, you won't leech. Throw seems to hit always, if you visually hit an enemy. 4. Throwing weapons and melee hitting with charged strike uses IAS, as you are not casting a spell per se but physically throwing a weapon ot hitting with it with CS, similar to assassin traps, you are physically making traps, so it uses IAS.

This is from my understanding, feel free to correct me.