Here is a compilation of various pieces of blood dk info. Essentially wowdb but specific to blood and verified in game as opposed to going off potentially incorrect tooltips.
Breath of Sindragosa – 100% AP to the primary target, 1/n% AP to all secondary targets where n is the total number of targets, including the primary target.
Example: 5 targets hit with BoS. 1 target will take 100% AP and 4 targets will take 1/5=20%AP
Blood Boil – current deals 1+108% AP (the current wowdb/wowhead entry of 60% is wrong)
Death and Decay – 1+12% AP per tick