3 words: Yes it does. You gain a bonus.
No you don't, you write data to the spell which isn't used until the spell actually goes off. The data write isn't "adding a bonus", it's changing a value to the result of an equation. No matter how many times you calculate it, the answer to 2+2 is always 4, and no matter how many times you change the values of a spell, it will not benefit you unless you actually use it. Begin cast triggers can only be abused when you place an action of self-contained value within the event trigger. Changing the data field of a spell is not self-contained value, it's a complimentary value. If you had a trigger that gave you 1 gold every time you cast a spell, having the event being "begins casting" would be exploitable, and thus, it'd be a very bad idea to use that event, but this simply isn't the case for a non-incremental variable assignation.
It doesn't fire at the beginning of the cast, it fires right before it. Just like (A unit is attacked).
It just sucks.
That IS the beginning of a cast, if you think about the casting process from start to finish, and not just the moment the spell effect goes off (that's how it's different from the other event to begin with). It's not like this event was included as an inferior alternative by mistake, it has it's own use which differs wildly from the effect event.
Also, we seriously need an (a unit is hit by an attack) event to match this one...
I don't know what you mean by this, but making spells cast instantly was always possible with a dummy unit and the cast backswing and cast point to 0 along with the real spell cooldown to 0.
And summoning a customized dummy unit to cast a spell and cleaning up all the odd mechanics, potential bugs, and terrain glitches, stemming from that as well as the memory leaks you need to clean is totally a more simple and straightforward approach than simply using a different event and a simple action. Come on man, you're grasping at straws here, you even go on to say:
It doesn't really ignore casting animations
Which means you admit that this far more complex and time consuming approach produces an inferior result. I mean, just why? Both methods have different applications, but in this particular case, going with the begins casting event is definitely a better choice in just about every conceivable aspect. I'm also not sure how a dummy cast would go off instantly without begins casting in the first place. What exactly is the event? Effect will never be instant unless you set the backswing and cast point to 0 on the main unit, and that would apply to all spells, not just 1. Far less controlled.
Somehow they screwed the instantly multiple target spells with dummies, it won't work in this patch anymore lol...
Yeah, I am officially avoiding this patch until Blizzard sorts it out.