Bloodlust Timing

Here is a very interesting theorycrafting discussion on when a raid should pop Bloodlust/Heroism. Should you Bloodlust early in the fight, or should you wait until 35%, when a lot of the extra damage Execute-style talents kick in?

Surprisingly, the answer turns out to be that it doesn't really matter! So the final conclusion is that the best use of Bloodlust is:

1. If there is no other factor, use Bloodlust early to maximize the number of people and cooldowns available.
2. If one particular phase needs to be burnt through in the shortest possible time, use Bloodlust then, and match cooldowns to Bloodlust.

Honestly, this result seemed a little counter-intuitive to me at first, but the math looks good. If you're interested, check out the algebra at the link.

Here's a "real numbers" example. Let's say there's a boss with 1,000,000 health. You can do 1000 damage-per-second. Below 35% health, let's say you do an extra 20% damage for 1200 dps. Further, let's say that Bloodlust boosts your damage by 30% for 40 seconds.

Case 1: Bloodlust Late

If you Bloodlust at the end, you do 1000 * 1.2 * 1.3 = 1560 dps for 40 sec.

1. Normal mode takes 650,000 Health / 1000 DPS = 650 sec.
2. Bloodlust for 40 seconds, doing 40*1560 = 62,400 damage.
3. Then you do the remaining 287,600 damage in 287,600 health / 1200 dps = 240 sec.

Total time to kill the boss = 650 + 40 + 240 = 930 seconds.

Case 2: Bloodlust Early

If you Bloodlust at the start, you do 1000 * 1.3 = 1300 dps for 40 sec.

1. Bloodlust for 40 seconds, doing 40*1300 = 52,000 damage.
2. Boss has 598,000 health until 35%. It will take you 598,000 health / 1000 dps = 598 sec.
3. Then you do the remaining 350,000 damage in 350,000 health / 1200 dps = 292 sec.

Total time to kill the boss = 40 + 598 + 292 = 930 seconds.

Conclusion

It doesn't matter when you Bloodlust during the fight if you just look at the bonus Execute-style damage and the extra damage from Bloodlust!

There are two advantages to going early. First, everyone can line up all their cooldowns like trinkets or Avenging Wrath and use them for maximum effectiveness. Second, it is more likely that everyone is alive at the start of the fight. By the time you reach 35%, you may have lost one or two people.

However, if there is a specific phase of the fight that needs to be shortened, then you should Bloodlust at the start of that phase. For example, even though the total fight lengths are the same, in Case 1 you only spend 280 seconds in the last phase, while in Case 2 you spend 292 seconds in the last phase. If a phase does increased damage, or has a separate enrage timer like Phase 3 of Prince Malchezzar or Lady Vashj, you'd be better off waiting for that phase before you Bloodlust.

To sum up from the linked article again, the best rules for Bloodlust/Heroism timing are:

1. If there is no other factor, use Bloodlust early to maximize the number of people and cooldowns available.
2. If one particular phase needs to be burnt through in the shortest possible time, use Bloodlust then, and match cooldowns to Bloodlust.