PSA: Bloodlust tiers are NOT "5% Haste."
This is a common misconception I see very frequently, even by people who are experienced and good at the game, so I wanted to make a post to hopefully inform some players.
Bloodlust is not equivalent to a 5% Haste buff. Bloodlust and Haste work very differently. What Bloodlust does is it adds a flat value of 0.2 to your base movement speed per tier. Haste, on the other hand, works by multiplying your movement speed by a value higher than 1.
This misconception likely occurs from the very common practice of measuring in-game movement speeds relative to that of a running survivor. If we have a linear scale where 0 represents standing still and 1 represents a survivor's default running speed of 4 meters per second, then a killer who moves at 4.6 meters per second--the base movespeed of most killers--then they would fall on the scale at a value of 1.15, or 15% faster than a running survivor. This is where the term "one-fifteen killer" comes from. What Bloodlust does is increase a killer's movement speed by adding a value of 0.2 meters per second to it, increasing your speed from 4.6 meters per second to 4.8, which on our scale moves a killer from 1.15 to 1.2, for a difference of +0.05, or +5% faster than a running survivor. Because this value of 0.05 is constant regardless of our initial speed, it's always going to be a difference of +5%.
This is where the misconception comes from: With bloodlust, you are not increasing your movement speed by 5%; you are increasing it by 5% of a running survivor's movement speed. A 5% Haste buff, which ACTUALLY increases your movement speed by 5%, works multiplicatively rather than additively. Normally your base speed is multiplied by 1, which just returns your base speed. A 5% Haste effect would increase this number by 0.05. On a 4.6/115 killer, this looks like (4.6 x 1.05 = 4.83). On our scale, this would move our value from 1.15 to 1.2075; comparing this to tier I Bloodlust's scale placement of 1.2, we can see that 5% Haste is actually slightly faster than a tier of Bloodlust.
If we wanted to convert Bloodlust's additive value to a multiplicative Haste effect, then a tier of Bloodlust would be more along the lines of 4.35% Haste, rather than 5%. It's not a big difference, but it's certainly not negligible, either.
Hope this post addresses a few misconceptions!