So I have been doing some tests on my own, because I always thought that AoE was better even with not that many creatures around. Seems like I have been wrong all these years.
I did my tests on my RP using normal bow and normal crossbow, and 1 powerful vampirism and 1 powerful void imbuement.
First I tested the difference when I attack a wyrm, which I don't Hs, and a cave rat, which I do hs, with crossbow:
| Crossbow and spectral bolts |
1 Wyrm (3 hits) | 600 hp = 150 life + 48 mana |
596 hp = 149 life + 48 mana |
840 hp = 210 life + 68 mana |
1 Cave Rat | 30 hp = 227 life +73 mana |
30 hp = 203 life +60 mana |
30 hp = 142 life +46 mana |
So, what I see, and I hope someone correct me if I'm wrong, is that you steal hp and mana according to the hit that you would be dealing to the creature if it had more hit points.
Next I checked the differences on cave rats but using bow and crossbow, single and multiple target:
| Crossbow and spectral bolts | Bow and diamond arrows | Total life and mana gain |
1 cave rat (single target) | 30 hp = 227 life +73 mana | 30 hp = 85 life +30 mana | |
30 hp = 203 life +60 mana |
30 hp = 142 life +46 mana |
3 cave rats at the same time | | 30 hp = 40 life +13 mana (to each one) | 120 hp 39 mana |
5 cave rats at the same time | | 30 hp = 25 life +9 mana (to each one) | 125 hp 45 mana |
8 cave rats at the same time | | 30 hp = 25 life +8 mana (to each one) | 200 hp 64 mana |
So according to this, it depends on the amount of creatures/players hit by you, would be better to use diamond/bolts.
Someone, better on maths than me, know when the use of each one is better, to maximize the steal of mana/hp?