There is no difference if you press one key and have three abilities fire off at once, and putting them all in one macro and spamming one key. Or using ISBoxer to fire off three macros separately by pressing one key, than if you put all three abilities on three separate keys and mashed them with three fingers.

There is no grey area.

Blizzard just doesn't want you to press one key once, have it do one spell at one moment, then cast another 2 seconds later, then another 3 seconds later, etc... all by pressing one button. That is called delayed actions and is against the blizzard TOS and EULA. Two completely different methods, one not illegal, and the other COMPLETELY ILLEGAL.

ISBoxer cannot send a delayed key presses to my knowledge, however keyboards like ones made by Logitech can. However blizzard cannot tell their players not to use those keyboards, only to not use those functions.

Basically, play within the rules and its more fun than playing outside of the rules and getting busted and having all your progress reset to zero cause your account is banned and you have to start all over