Additive or multiplicative?

[Kaysha]

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%)?

[Xelaeno]

you multiply them

it goes like this:

(spellpower cofficient * spellpower + tooltip avg number)*1.05*1.10*1.03*1.10 = CoH total output

healing bonus are multiplicative, same goes with dps damage numbers

[Danner]

They changed the mechanics in patch 3.0. Before WoTLK hit us, you added together bonuses of the same "level". I never quite understood which buffs were on the same "level", but I still remember that Searing Light and Force of Will were additive, not multiplicative, while the zonewide buffs were always multiplicative, and setbonuses seemed to be a bit of both. Luckily, that's no longer relevant ;D

Nowadays, you just multiply everything. Easy to work out; a 5% buff is a 5% buff.

The only exception is the "empowered" talents (empowered healing, empowered renew) which only multiplies with your spell coefficient, not the final result. A lot of people are still fooling themselves thinking Empowered Healing is awesome as a result :P


EDIT: Actually, that's not quite true. BoK and Spirit of Redemption are still additive. Meaning you get a 15% buff with both, not a 16.5% buff. I guess there are still some additive stuff in there :P

[Kaysha]

Thanks for the info, I searched around with Google, but couldn't really get a clear answer on composition of the various boni. This helps solve it :P.

And I am purely looking at myself, completely unbuffed for now. I will take another measure of my healing potential when fully raid buffed (should have done that earlier tonight ) and check how regemming changes those values.

Fully unbuffed, I am underwhelmed though on swapping out gems. I'd lose out on about 6 to 10k mana on a 6 min fight if I swap out my Spirit gems from pure SP (or SP / Int, SP / Spi), while only getting about a 3-5% boost in total healing power across all spells.

Actually I also need to check this against total number of spells I cast during a boss fight. I think the difference will be marginal, however.

[Xelaeno]

The only exception is the "empowered" talents (empowered healing, empowered renew) which only multiplies with your spell coefficient, not the final result. A lot of people are still fooling themselves thinking Empowered Healing is awesome as a result :P

jeez now i feel cheated, how i was fooled o.O" (but wait, i have an excuse! i don't play healz much ;D)