Damage Block vs Armor: Mechanics and Situational Use

Damage block and armor both reduce the damage taken by your hero, which is quite important as this can be the difference between a glorious kill or an embarrassing death. Surely though if they both stop damage then they can’t be that different? A closer look reveals there is in fact a world of difference, between both the mechanics behind them and the appropriate situations for them.

There is a dangerous amount of maths in the mechanics explanation, so you may just want to skip to the end where I compare them and talk about their situational use.

Damage Block - mechanics

Damage block gives a percentage change to block a fixed amount of physical attack damage from each incoming hit. So whilst it blocks creep attacks or a hero’s right click attack, magic damage from spells or other damage types will be unaffected. Stout shield, vanguard and poor man’s shield all grant this ability at different percentage and damage values.

Stout shield: Costs 250g and gives a 60% chance to block 20 damage for melee heroes and 10 damage for ranged heroes

 

Poor man's shield: Costs 550g and combines the stout shield with two slippers of agility to give +6 agility and 100% chance to block 20 or 10 hero damage for melee and ranged respectively and a 60% chance to block 20 or 10 non-hero damage for melee and ranged.

 

Vanguard: Combines a stout shield with a ring of health and vitality booster for a total cost of 2225g and grants +250 health, +6 hp/s regeneration and a 70% chance for melee heroes to block 40 damage and ranged heroes to block 20 damage

 

There is talk about the use of a pseudo random number generator (PRNG) lowering the actual block percentage chance but it appears PRNGs are not used in Dota 2 so the percentage advertised is the one you get. This damage block also occurs before any reduction of the damage from armor value i.e. if your melee hero takes 100 damage with a stout shield and five armor (five armor giving ~23% damage reduction) there is a 60% chance to take 61.6 damage (100 – 20 = 80, 80 reduced by 23% to 61.6) and a 40% chance to take 77 damage (100 damage reduced by 23% = 77).

You can also stack this block damage, with the last damage block picked up calculated first followed by the second last and so on. The damage reduction percentage is calculated by 100% – [(1-x)*(1-y)...] where x is the last percentage damage block chance and y is the second last etc. It can also stack with abilities such as kraken shell on Tidehunter and Mana shield on Medusa but make sure to drop your damage block item and pick it back up after each kraken shell level or activation of mana shield to ensure maximum blocking potential, although this may change with Medusa's implementation into Dota 2.

 

armor - mechanics

armor reduces the amount of damage a hero takes from an attack. How much this damage is reduced depends on the units armor value as well as the type of damage being done. There are six major types of damage that scale according to the armor of the unit taking damage. We are only concerned with Hero type armor here, so only those values are shown.

Damage type Percentage of damage taken (before reduction by armor value)

Normal 75%
Pierce 50%
Siege 75%
Chaos 100%
Hero 100%
Magical 75%

This means that even at an armor value of zero a normal attack with only do 75% of its full attack damage to a hero. Running around with no armor like a naked snail isn't helping anyone but your enemy, but a heroes base armor value can be increased either through pure armor (like chainmail) or by agility with every point of agility increasing armor value by 0.14. Note that increased armor value only reduces physical damage dealt, not magical and other damage.

Now you've taken that advice to heart and just bought your fourth assault curiass, but how much damage is your armor laden hero taking? Damage reduction is shown as a percentage in your stats in between your hero portrait and items. If you don't trust this figure or want a more exact number you can calculate your damage reduction using the fomula (0.06 x armor)/(1/(0.06 x armor)).

armor value is often also talked about as effective hit points (EHP). Every point of armor means your hero will have to take an extra 6% of their max health in damage to be killed. This means a hero with and armor value of 10 and 1000HP will have to take 1600 attack damage from an enemy hero (10 armor at 6% each is 60%, 60% of 1000 is 600 for 1600 total).

What does all that mean?

So that's how they work but when are they actually going to be useful? Damage block is a fixed value and so is most effective early game. The 20 damage block is going to be much more effective at level one when enemy heroes are only going to be doing ~50 damage (a 40% reduction, which would require an armor value of just over 8). So if you're a strength or agility melee carry and expecting to get harassed you should definitely consider a stout shield as a starter item, especially if you're running a solo lane or jungling.

'But what about ranged heroes?' I hear you ask. Ranged heroes only receive half the damage reduction of a melee hero and if you're attacking and positioning is good you should be taking minimal damage. It's almost never worth picking it up as a ranged hero as even if you are getting harassed there are better items than stout shield for survivability.

As damage block gets weaker, armor become more effective as the game goes on. Because the damage reduction of armor is percentage based, the more damage an enemy hero does, the more damage is blocked. If a hero has an armor value of 5 (~23% reduction, this is the last maths I promise) it will be doing much more for you if your enemy does 300 damage rather than 50 (69 damage compared to 11.5). High armor values are useless if enemy heroes have a low damage output because a high percentage of nothing is still nothing.

If the damage you're taking is mostly magical it could be worth giving armor a miss and picking up a Hood of Defiance instead, but against a late game Phantom Assassin or Anti Mage with a 1k crit because they've been fed all game armor is your best protection for going in for a kill or just surviving until the next team fight. A lot of the big armor items like Shiva's Guard are items you'll be picking up later on in the game anyway but if you find yourself with a few thousand gold at the fifteen minute mark after a few easy kills, damage or health items are a better idea to pick up first.

Thanks for reading guys, I hope that wasn't too dense. Stay tuned for more Dota info!