If you look at the Observer action clip, the air units are cloaked banshees, but their rockets seem to have single target attacks dont you think? http://www.starcraft2.com/features/protoss/observer.xml
I believe that the Bannshees have massive attack vs. smal units , and vs. large medium and building have single target.
Nah, its pretty obvious the banshees shoot the same way vs the probe(small) the building(large) and the stalker(i think medium) so i don think thats it.
Hmm, they really did tone down the Banshee attack. They could have toned it down purely for demonstration purposes, but I don't really see the need when it's the Observer that's being showcased. I don't really see any other reason as to why they would have weakened the Banshee's attack, it didn't seem to imbalanced IMO.
I think they made have changed the attack animation to look a little more powerful as before it looked like little pellets. Same attack effect, though.