A question about client vs server?

[savaughn]

The question was not of control. I assume everything is server controlled (and with some bad exceptions in the start, most was in D2 also actually). What I asked was if the client calculated things in parallell. This can be good if you want to prevene lag effects. If the server tell the client the stats of the player, the client can for example calculate (assuming it has the ability to "parallell" calculate) estimate with a good accuracy if a spell will hit, what the damage will be and so on. Obviously it then updates with the server's result, but that was not my question.
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Again, a very few things yes, most things no.

The client won't start a spell without a response packet from the server and won't land a spell without a response from the server. Similarly you can't start an attack without a response from the server.

Once a spell or attack has started, however, the action will continue on the server and the client will attempt some prediction, updating with the server data. This is really only noticable during periods of extreme lag. Overall, very little is done in parallel. The reason for this is obvious - the positioning is critical for combat and changes constantly making predictive values nearly impossible.

<edit: as a side note, it looks like (just based on observation) that Blizz has chosen not to do a parallel random number generator, meaning that client side you can't predict the next random number. This means it's impossible to hack to see if you're going to miss, but also means only the server can send that info>