Dota-Allstars Critical & Bash Guide

Dota-Allstars Critical Strike & Bash Guide will be posted here. This guide is made byMalle from www.dota-allstars.com , all the credit belong to him. Both critical strikes and bashes stack with diminishing returns, as according to the formula: 1 - ( 1 - A ) * ( 1 - B ) * ( 1 - C ) .... ( 1 - X ) = Chance to bash / critical strike where A, B, C and so forth are the seperate chances for each item or skill that can bash / critical strike. When calculating damage from critical strikes, if two occur at once, only the last critical strike skill or item you achieved will have effect. Skills are only counted as achieved when they are learnt for the first time. When calculating bashes, it depends on whether you're a melee or ranged hero. It is universal though that if the bash time you should apply is less than the bash time the opponent currently has left, then no change in the bash time will be made.
Melee heroes' bashes stack fully, where if two bashes occur at once, the longest stun time from all of the bashes, and each and every seperate bash's damage will work. The damage is reduced by armour type spell resistance (and eliminated by magic immunity), but the stun is not blocked by magic immunity. The damage is counted as a seperate source, and does thus not affect lifesteal, nor is it affected in any way by criticals.

As for ranged heroes, if two bashes occur at once, only the bash time and damage from the last bash skill or item you got will work. The damage is hero type physical damage, that means it's not blockable by magic immunity and it's reduced by armour type hero resistance and armour value. The stun, however, is blockable by magic immunity. The damage is added as your normal damage, but will be skipped if a critical triggers after it (essentially the damage you deal will be BaseDamage*CritMultiplier). If the bash instead triggers after the critical, the damage will be added after the critical strike has multiplied the normal damage. (BaseDamage*CritMultiplier + BashDamage)

Note: As of 6.28, Banehallow does not count as a ranged hero in his ultimate form. As of 6.44, Ursa no longer counts as a ranged unit either.

As it seems some people have misinterpreted what I've said, I'll try to clarify a bit more.
When it comes to bashes on melee heroes, the formula above only tells you the percentage to get at least one bash on an attack. As melee heroes can get multiple bashes on each attack, all bashers can still trigger on the very same attack, meaning that they would all do their bonus damage, but only the longest stun time would be used. This in turn means that on melee heroes, the damage you get from a basher does not decrease if you get more bashers.