Firestorm

It's currently 1.5ms (0.0015 seconds) per % quality. 0.2 seconds would be insane, and would have completely removed the delay at only 8% quality (delay is 0.15 seconds). A 20% quality firestorm would be removing four full seconds from the 0.15 second delay between fireballs, thus dropping them backwards in time.

The wiki is not an official resource which we have any hand in updating, so anything on the wiki should be taken with a grain of salt as it is often out of date, and occasionally just subject to errors as in this case (which is not to say it's not a useful resource a lot of the time, just don't take everything you see there as fact).

Because that gem adds a percentage of the skill's physical damage to fire.
Firestorm does no physical damage.