Double Strike can miss on 2nd strike also on a repeater. If I am not mistaken I would call the Night Reaper a repeater.
Double Strike only goes off if the first strike lands and the 2nd hit has the same chance to hit as the first strike. It will miss even if the first strike lands.
I am not sure the difference between the two (i think they are the same). They made Double Shot requiring the user to be mounted and a secondary skill is probably the trade off for having Double Strikes on a slow hard-hitting weapon.
Also another thing to note, you can have direct hit damage spell go off twice if both shot hits but the double hit spell will not happen on any "delayed" spell types. So far I was able to do double shot with double lighting/harm proc (4 damage numbers) but never happened on hit magic arrow nor hit fireball.
I imaging if you can score a good yumi with hit lighting and velocity you can probably see 6 damage numbers in a single attack which could be devastating. My personal record on my archer with a hit lighting yumi using double strike was 68 total damage in 1 shot. That's against a guildie with all 70 resist without curse.
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