Do charm damage stack? Say I have one charm that does 1-10 cold damage and another charm that does 2-15 fire damage. How are the damages applied.
Also, for life leech, if say 7% life leech, is that per hit? What if I use a bow and use multishot and my arrows hit 4 targets. Is it 7x4=28% life leech, or is it capped?
Thanks.
Life leach is only for the physical damage you deal, damage charms only apply to physical damage attacks excluding smite.
If you deal 100 damage per arrow your u hit with you will gain 7 life per arrow
7% of any physical damage you do on the target. But keep in mind that some foes are immune to it. Like undead.
Life tap curse solves the issue in that case, unless the target is also immune to physical.
Considering the arrow hit 4 times and didn’t got blocked you with leech 7% on each arrow not exactly the 28%. Because each arrow has their own damage range and are subject by AR, Block, damage range but also physical res from the target and the difficulty you’re in.
By example if your physical damage are 100-200 and the foe has 50% physical res. Your effective damage would be 50-100. Keep also in mind that on hell by example the amount stolen drops by a third of the value.
So on normal would be 3.5-7 while on hell 1.167-2.334 in that monster with 50% physical res.
Some multiple hit skills show the sum others show per strike. Multishot would be each arrow but only one arrow can hit each target. So in the end, if there’s only one foe, multishot isn’t a great skill to use.
Strafe on the other hand could be more interesting, but often has less value than guided arrow by example.
melee and Life-stealing feel a most useless and die after patch 1.09 , a most better to stack Replenish Life . caster all the way 
and also get nerf a other time i dont rememeber