Arrow flight time?
 

I notice that arrows seem to hit instantaneously. Granted I don't have much range, but I see an aggro reaction the instant I shoot, and *then* I see the arrow fly out. I don't recall that from classic, but maybe I have forgotten. Is it supposed to be that way?

Are all missile type attacks that way? I.e., thrown stuff and bolt spells?

Nope that is a p1999 exclusive

Perhaps they see you pointing your bow at them?