Display Morehmmm, seems it's really bugged, and it also happens with other spells, if you flooding the same spell, at one moment it breaks, but if using spells in sequence like shot vampire joint it works fine, without any delays after skill is ready.
If u use it once in a rotation without spaming or sth it can work but you need to link it to be prio in some way, so no other hits can be done without snake poison beeing on the target but if it comes to spamming the skill it breaks after few hits and buggs out (even if placed as total prio and with the condition of snake posion beeing applied on target etc)
-> delays happen for some reason e.e
Also atk speed sadly seems to have bad effect on this somehow (makes it worse, even tho it should make it better -> more hits because of higher atk speed but nope instead you gain 2-3 hits 1-2sec lag 1-2 hits lag etc and also even with same atk speed over a longer time the skills sometimes gets out faster and sometimes with some lag (thats what you can see in the vid with pure red 1sec red and totaly up without beeing used even tho ITS first prio skill in macro with a lot of work put into (was working fine until one patch as i said but everything i did was not able to fix it and other players have simular problems )
Hope this explains more on what this problem is rly about maybe some dev might be able to give further info about fix etc
But yeah in sequenz for boss it works fine with all the conditions but for aoe rotation sequenz with other spells it doesnt work good in any way becuase of it coming out with sutch inconsistance even tho it clearly is meant to be spammed in AoE rota.
You can try use Joint Blow after Snake Poison in your aoe rotation