Your positioning matters a lot more because unlike Destro and Affliction you are lobbing relatively slow cast nukes and only have 2 instant casts (corruption/CoD) to keep up. You may even want to adjust how you life tap and avoid tapping during the times when you got all your buffs up unless its to keep your glyph and set bonus active. Make sure to have those buffs up going into execute phase and have enough mana available so you can just lob soulfires the whole time.