Hi,
Yesterday I got an 396 wand and equipped in in exchange for my 150 wand. According to the numbers I expected more than doubled damage than before. But it seems just a little higher.
Weapon damage is scaled to your level. So you will only be doing a marginal amount of MORE damage with the 396 wand.
You can see just how much more damage you are dealing by going to the practice dummy and shooting it with both wands. You should not expect to see more than 10-20 damage increase from your spells.
There is a cap to how much of the attack stat you can take advantage of at a given level. So if your cap at level 11 was to be 200 (made up number), then both a 396 wand and a 500 wand would give you just as much attack.
Keep in mind that intellect is not capped this way. So for two wands that both have more attack than you can benefit from, the one with the most intellect will be the best to use.