All arrows would be equally aimed, since the spell-generated arrows are aimed at the same target (the wait is to give time to improve aiming, and wait for an opening). Otherwise, why wouldn't the magically-created arrows attack at a fixed percentage chance, since an improved skill % means an improved ability to target, just like the effect of waiting?
As a minor rules variant, we always played that the wait was random for each person and each time, but that no other actions could be made before the end of the preannounced wait (a mini-arrowtrance effect, sort of). This prevented rules-gaming like having an entire party attack some giant or Rune Lord at the same strike rank to prevent it from parrying more than one blow. The DM rolled the waits secretly, and told each player to attack on the rolled SR. It had the nice effect of simulating in the player's mind the effect of an opening suddenly appearing, as well as preventing the illusion-ruining perfect coordination of attacks. You could also delay just to delay, but that actually lowered the attack % by 1/3, as you would be adversely affecting your usual timing and flow of movement.
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