Let's get some layman terms here so I am understanding this.

using cast sequence completely skips some intended or unintended delays in the game/server?
using a micro delay like .3 re-enables this or enhances this?
and is having say 2 spells on your action bar 1 and 2, if you mash both at the same time. Is the cast sequence with delays even faster?

I suppose trying to understand here what this is achieving.