I played XI and running around to cancel a spell didn't always work either.
I do not like the idea of implementing that in this game, being able to run while casting is great.

They just have to make a button that cancels any spell. Or an existing "cancel" button to stop spells only when casting.
Such as pressing escape on keyboard would stop a spell in casting. I don't use a controller for this game but surely there is a "cancel" like button on it.. for menus and whatnot.