I'm currently evaluating and considering my gemming and enchanting and all that jazz. Of course, this influences my healing output as well. Way back in TBC I used to have an Excel sheet with which I held a firm grasp on my healing, but I've since lost it.
The one question that I have about it though, is this: are the various healing boni additive or multiplicative? When for instance I am looking at Circle of Healing, it receives the following boni (in Holy spec) to total healing done: 5% from Twin Disciples, 10% from Spiritual Healing, 3% from Blessed Resilience and 10% from Divine Providence.
Would the total then be 28% (5% + 10% + 10% + 3%) or rather 30,86% (5% * 10% * 10% * 3%)?