You could walk/que into a Solo, take some damage and then use Soul Siphon on 4 targets to see the full capacity of it. If you use it as a standalone heal it may not seem as great. it's best used in conjunction or preferably clipped with Rejuvenate. SS + Rejuvenate = Burst Heals, Rejuvenate hitting the lowest ally, and additional Healing ticks from Bad Karma. That comment was directed toward other powersets, not so much Sorcery. There are other weapons like MA, Rifle, and the Shield that shorten or even clip power animations in other powersets.