With some more info put forward to me Zachary here on blogger there needs to be a big update.
tldr:
Blood Boil is only better than Heart Strike depending on AP, Weapon Damage and the number of targets:
Here is an example with a 31,170 average Weapon Damage weapon.
The Math:
The big there here is that Weapon Damage is also modified by AP. (4.24 AP = 1 Weap Dam)
So the question now: How many targets do I need to have before Blood Boil will do more damage than a Heart Strike?
Heart Strike Damage on Three Targets = Blood Boil Damage x Number of Mobs required.
((545 + Weap Dam x 1.05) x 1.3) x 1.75 = ((3859 + AP x 0.11) x 1.5) x M
M = ((545 + Weap Dam x 1.05) x 1.3) x 1.75 / ((3859 + AP x 0.11) x 1.5)
As a result depending on Weapon Damage and AP (base and from Vengeance) we can find the number of mobs required.
Here is a spreadsheet I've made up with the basics:
