I leveled a wand character to level 29 and I must say there is some truth about wand user scaling up better at higher levels, at level 29 I could spam 5-6 rank III spells consecutively without SP pots as the higher WIS stats meant a higher max SP pool, SP regen and possibly lower SP cost for skills(cant quite point my finger on all the factors that affect this but take a look at my screenshot on this thread
viewtopic.php?f=10&t=2488 - 100 and 98 SP cost spells costing less than 62 Sp to cast, 4th post).
I soloed all bosses in kyoto when I was around level 25-28, and could have probably done it on lower levels but with alot more kiting and SP pots. However, I must add that from what I know up to the end of cbt, bow users could achieved the same results or better with probably less effort, though the gap between the two ranged classes had slighly been reduced in the late 20s. Hopefully wands do catch up later on.
Use SP pots(1-5 is usually sufficient for most dungeons). Wand users need to Spam SP pots while melee users are more likely to spam more HP pots and bows have durability issues. I guess thats the trade-off.
My point here is that SP cost/consumption isnt the issue for me. This problem seems go away in later levels but the issue I have with wand users is the damage output. Bows deal much higher single target damage but at the same time, wands have pretty crappy AOEs( there are a FEW decent aoes but cant even be compared with the odachi, heck even some of the bow aoes can compete with it). If the aoes were great id be happy but it seems that the wand just doesn't excel in anything at the moment.