Evasion, Miss, and Dodge Stacking Guide

There are currently 4 types of methods to Dodge damage. These are Evasion, Miss, Terrain Advantage, and Triggered (a.k.a. Pseudo-Evasion, Heal). The way to calculate your total chance to Dodge damage is
P = 1 - (1 - E) * (1 - M) * (1 - T1) * (1 - T2)
Where P is your Probability to Dodge damage, E is your chance for Evasion, M is your opponent's chance to Miss, T1 is your opponent's chance to "miss" due to Terrain disadvantage, and T2 is your chance to avoid damage due to Triggered Evasion. Each of the four factors (Evasion, Miss, Terrain, and Triggered) work independently of each other. As such, a source of Evasion will always stack diminishingly with a source of Miss or Triggered.

To give precise definitions, "Dodge" refers to your total ability to avoid taking damage. "Evasion" refers to skills or items which gives a percent chance for Evasion. "Miss" refers to skills which cause an opponent to Miss on a certain percentage of attacks. "Terrain Advantage" refers to a ranged attacker being below the attacked unit. "Triggered" refers to a JASS triggered ability to avoid damage. "Normal attack" refers to a hero's attack command, i.e. pressing A and then clicking on a hero, or auto-acquiring a target.

Evasion
The first type of chance to Dodge is Evasion. Evasion comes from items like Butterfly and Radiance, and skills like Jinada (Bounty Hunter), Drunken Brawler (Panda), Blur (Phantom Assassin), Phantom Edge (Phantom Lancer). Evasion does not stack with other sources of evasion. The highest source of Evasion overrides all other sources of Evasion. So if Phantom Assassin with 4 levels of Blur (28% Evasion) obtains a Radiance (8% Evasion), she will have 28% chance for Evasion. If she obtains a Radiance (8% Evasion) and a Butterfly (30% Evasion), she will have 30% chance for Evasion. Evasion only works against normal attacks.

Miss
The second type of Dodge is Miss. Miss is typically a debuff on the opponent which causes them to miss. This comes from spells like Smoke Screen (Stealth Assassin), Laser (Tinker), Blind (Troll), Drunken Haze (Panda), Incapacitating Bite (Spider), Crippling Fear (Night Stalker). Laser, Drunken Haze, Incapacitating Bite, and Crippling Fear do not stack with each other, but they will stack with Smoke Screen and Blind. To calculate a total chance to Miss, use the same 1 - (1 - A)*(1 - B)*(1 - C) formula. Miss only works against normal attacks.

Terrain Advantage
The 3rd type Dodge chance to miss is Terrain Advantage. Terrain Advantage occurs when a ranged attacker attacks uphill. Currently, this is a 25% chance to miss. Terrain Advantage only works for normal, ranged attacks.

Triggered
The 4th and final chance to miss is Triggered, a.k.a. Pseudo-Evasion, a.k.a. Heal. Triggered evasion works different depending on the skill. Currently there are 5 skills on 4 heroes that have a triggered chance to miss damage.

Craggy Exterior on Tiny, the Stone Giant--Tiny has a skill known as Craggy Exterior, which gives a 6%/12%/16%/24% chance to stun a melee attacker when attacked. In the case of Craggy Exterior and another Dodge proccing on the same attack, Craggy Exterior will take precedence. Craggy Exterior only works against normal, melee attacks.

Backtrack on Darkterror, the Faceless Void--Darkterror has a skill known as Backtrack, which gives him a 10%/15%/20%/25% chance to heal him for the amount of damage that he would normally take. In the case of another non-Triggered source of Dodge proccing on the same attack, Backtrack will lose precedence. Backtrack works against all sources of damage, including spells and triggered damage.

Dispersion on Mercurial, the Spectre--Mercurial has a skill known as Dispersion, which has a 4%/8%/12%/16% chance to heal Mercurial for the amount of damage taken and also deal this damage back in a 400 AoE around her, as well as give a small stun. In order for Dispersion to work, the incoming damage must be greater than 5. If Dispersion procs on an attack which deals more damage than Mercurial's current HP, only her current HP will be reflected back. In the case of Dispersion and another non-Triggered source of Dodge occurring on the same attack, Dispersion loses precedence. Dispersion works against all sources of damage, including spells and triggered damage.

Aphotic Shield on Abbadon, Lord of Avernus--Aphotic Shield gives a 100% chance to heal over damage dealt to a unit. In the case of Borrowed Time and another non-Triggered source of Dodge occuring on the same attack, Aphotic Shield will lose precedence. Aphotic Shield works for all sources of damage, including spells and triggered damage.

Borrowed Time on Abbadon, Lord of Avernus--Aphotic Shield gives a 100% chance to heal over damage dealt to a Abaddon. In the case of Borrowed Time and another non-Triggered source of Dodge occuring on the same attack, Borrowed Time will lose precedence. Borrowed Time works for all sources of damage, including spells and triggered damage.

Notes
-The 4 heal type Triggered Evasions will only heal over the damage dealt in that attack. If the attack were say, a bash, or had a slow orb on it, they would still be bashed or slowed respectively. This is not the case with Craggy Exterior, as no attack actually lands on the hero.
-Craggy Exterior deals a stun (or has a chance to, rather) at the beginning of the attack animation. Other sources of Dodge are calculated at the attack point, which occurs after the start of the attack animation. This effectively means that Craggy Exterior takes precedence over all other sources of Dodge.
-In the case of a Heal-type Triggered Dodge proccing on the same attack as a non-Triggered Dodge proccing, the hero is healed for 0 damage. Note that this is below the minimum 5 damage for Dispersion to trigger, but will still give the animation for backtrack.
-For Dispersion, Aphotic Shield, and Borrowed Time, a rather lengthy series of triggers determines the correct amount to heal. This is not the case with Backtrack, where the heal is simply dealt before the damage is taken.
-For any of the Heal type Triggered Dodges, if an incoming attack deals more damage than the receiving hero's maximum HP, the hero will die.
-If two Heal type Triggered Dodges proc on the same attack (i.e. Abbadon has Borrowed Time and Aphotic Shield on, or if Mercurial Disperses while having an Aphotic Shield on), the hero's HP will rise. What happens is that the hero is healed twice for only one damage.
-In the case of Mercurial obtaining a Butterfly, Dispersion loses precedence to Evasion. What this means is that she has a 30% chance to Evade and an 11.2% chance to Disperse. This means that if her HP is 1000, and a series of 10-dmg attacks are dealt to her, without a Butterfly it would require approximately on average 119.05 attacks to kill her, and that 19.05 would be Dispersed. With a Butterfly, it would require 170.07 attacks to kill her, with 51.02 being Evaded and 19.05 being Dispersed. Note that she will disperse the same amount of attacks regardless of if she has a Butterfly or not. The loss of dps from Dispersion is perfectly balanced with her added survivability from Butterfly.

Original poster
ICallBotSolo in dota allstars forum.