On my healer commando, I obtained some mods to increase my Alacrity. I understand that it increases the speed at which abilities are casted, but what exactly does that mean.
An example of a casted ability is Mortar Volley for the Trooper (Death from Above for the Bounty Hunter). Without any Alacrity, that move takes 3 seconds to complete. With 5% Alacrity, it will take 2.85 seconds (
(1 - 0.05) * 3).
Since the 3.0 patch, Alacrity affects virtually everything: Cooldowns (internal timers, the Global Cooldown (GCD), and ability cooldowns), cast and channel times, tick speed of channels and Damage over Time (DoT) abilities, etc. As such, 1% Alacrity is essentially a 1% increase in Damage or Heals Done per Second (DPS/HPS). This is a bit simplified, since using Alacrity means giving up other stats you could use instead, but overall Alacrity is now very useful.
No, that is not how that works.
If it did, that would mean 100% alacrity turns your GCD and other Cooldowns into thin air. You would be a god capable of killing anything instantly.. because for all the game cares you could unleash a billion attacks in a millisecond.
Alacrity increases the speed at which you operate. It doesn't Multiply, it devides.
That means a 3sec ability would not be done 5% faster flat out, but rather be done at 105% of normal operating speed. Thus turn the ability into 3/1.05=2.857 seconds.
Doesn't seem like a big deal with these small cooldowns, but once you apply it to a 3 minute one you'll see there is quite a difference between the 2 manners of calculating it. And I assure you mine is the right one.