Question about attack speed

I knew that our green potion somehow glitched and able to break the cap. Then as the viewpoint for KMS.

I heard that most classes can just max out their attack speed with just their own buffs, then may I know what is the point of releasing DSI and IA-AtkSpd? It is just specifically for those class like Battle Mage?

I don't know where you heard that most classes can max out their attack speed with just their own buffs. As far as I know, most can't, (with their normal weapons, anyway).