Leech and Siphoned effect.

[Arktic]

Hello, Recently i've come across a problem and i don't know if it's just from my side or not so i'd like to ask any fellow warlocks about it. The thing is, When i use leech the animation will suddenly cut out after a second and i won't get the siphoned effect. However the cooldown on leech comes up. While leech is casting i don't toggle any other skills however i'll move left or right sometimes to avoid an aoe. Am i just supposed to stand still? I've not tested this is pvp, however it happens app. two or of three times i use the skill. My lock is only level 37 right now and the skill is set at it's base with no skill points added yet. Any help would be greatly appreciated, Thank you. 

[rocdog]

It's not an instant cast - 0.1 second cast time - so moving will interrupt it.

[Arktic]

I see, So i'm moving too soon. Thank you very much.