Yes and no, it would possibly save us from the gear delay /waits, but the cast delays so abilities don't step on each other would still have to be present.
In XI they were also stored/executed from the client and like it was said a little earlier except for the possible hax, if they were fully processed on the client side they'd be just as fast/smooth, but even then we'd need /waits for cast delays and things.
If the client didn't stop sending commands randomly during a macro it'd probably be enough, but that's that whole not getting fixed til 2.0 lag/latency thing getting in the way.