Well normally you light attack between skills, because LAs (unlike skills) are off the global cooldown so you can do damage with the LAs, while waiting for the CGD. However, since siphon has been now taken off the GCD, you can just click it between two skills. In truth, I still weave it with LAs just out of habbit, but you don't have to, and this way you can squeeze more skill casts in. As for when to cast it, I do it once per rotation, after it explodes, so I can get the benefit of the extra damage from the explosion.
Well normally you light attack between skills, because LAs (unlike skills) are off the global cooldown so you can do damage with the LAs, while waiting for the CGD. However, since siphon has been now taken off the GCD, you can just click it between two skills. In truth, I still weave it with LAs just out of habbit, but you don't have to, and this way you can squeeze more skill casts in. As for when to cast it, I do it once per rotation, after it explodes, so I can get the benefit of the extra damage from the explosion.
Just little correction. LA's dont trigger global cooldown but they are still disabled (like skills) when its in progress so you cant use LA while waiting for GCD.