Firestorm

Patch 2.4

Blizzard wrote:

Firestorm

• Casting Delay will no longer share its cooldown with other skills that have Casting Delays

• Tooltip updated to now display Casting Delay

If you are playing in Resurrected mode, this ability's projectiles provide a small radius of light, illuminating the dark slightly.

Per the Amazon Basin Wiki:

Fires three piercing missiles that leave trails of fire in their wake. Each of these missiles travels for 40 frames (1.6 seconds): the central missile travels in a straight line towards the target, while the other two follow more random paths. However, when cast continuously the three missiles will follow the same paths each time if the point targeted doesn't change.

Each missile spawns static fires in the third frame after casting and every other frame thereafter until expiry, spawning 19 fires each or 57 in total. These fires apply damage.

Firestorm has a range of ~10 yards, but is best cast at a target at point-blank range.

Displayed fire damage per second is calculated based on three fires applying their bit rate every frame of a second (3 * bit rate * 25/256). Each fire actually applies its bit rate for just 14 frames (bit rate * 14/256): however, it's been observed that up to 5 fires apply to size 1 targets, up to 9 apply to size 2 targets and up to 14 apply to size 3 targets.

Due to its comparatively short delay,

Firestorm will be cast at least once per second and Faster Cast Rate can increase that frequency: actual fire damage per second can be up to twice that displayed for size 2 targets and up to triple that displayed for size 3 targets.