Since there are both skills and pieces of equipment that improve casting speed, I think it is important to learn what this actually is. Does it mean spells are delivered more quickly? does it increase spell dps? Anyway, forgive my ignorance and thank you in advance.
Cast speed is essentially the speed it takes to deliver spells. Spells or skills like panetti, forcewave, phantasmal blades etc. . skills that does not require weapon contact to enemies. It does what attack speed does to weapon contact based skills like cadence or primal strike.
as a result of the increased in cast speed ultimately your dps will increase because now you generate damage faster.
and even if you cast spells with cooldown, having larger casting speed makes the animation shorter and the gameplay will be more fluent
Thank you!