To really use WoD you need a good arcane focus. The higher the focus the earlier you can cast, this is based on how much life your tgt has left. Each level of focus adds 5% to the amount of HP your tgt has left before WoD is effective. For example the Dark Father has 30,000 HP to start so at a level 2 AF your WoD will start working when he has 3000 HP left or 10% of his total. Level 3 would be 15% and so on up to level 6 at 30% or 9k HP. Now your SW skill only effects your chance to cast not damage output, you will need SDI on your character to boost the damage output once in the WoD range. If you are trying to use WoD without an AF or on low level monsters don't bother.