how are you doing similar damage to yourself to harm them? what force are you casting your direct combat spells at, exactly, that you can't soak the drain on a spell that realistically has no business going above a force of about 5-6 unless you have a truly ridiculous amount of karma under your belt to actually need the higher limit?
and the main problem with magicians is that, right out of chargen, they can have all of the dice pool they need to be effective. from the very instant they're created. oh, they can get better at it, but that's just gravy. you can start off with a powerful focus, your key skills at a high value (perhaps not every one maxed out that you'd like, but that's everyone), and an excellent magic attribute. where this becomes a problem is just how much of that immediately becomes applicable to any new spell they acquire.
a combat magician might throw 16-18 dice on combat spells... and probably throws 14-16 dice on every other type of spell, also. which means that the mage focused heavily on combat needs to spend only 5 karma to pick up influence and is suddenly as useful as a powerful face as well in many circumstances, while the street samurai needs to invest in a completely different attribute from the main focus and pick up half a dozen skills to accomplish the same feat. *that* is where the power comes in. a simple 5 karma investment takes you from 0% effectiveness in many fields to being close to as good as an expert in those fields. magicians have bad initiative? 5 karma later, your magician can actually have pretty good initiative, all it takes is learning the right spell and using it. your perception is not so good? 5 karma later you can spot enemies from hundreds of meters away through walls or when they're blending in with a crowd.
whatever you do as a magician, it is very likely that by simply spending an additional 5 karma, a sizable portion of the investment you made towards doing your main focus can be applied to a secondary focus. this is less of a problem for adepts, i'll admit (in fact, i'm quite happy with the current situation between pure adepts and pure street samurai, although augmented adepts i think may pose a slight problem in being able to make better use of all available resources... but overall, it's close enough that you're not losing a lot generally speaking between choosing one route or the other).
it works out to be not too bad in chargen, because the current increased cost of that core (magic + spellcasting is generally more expensive to get high in chargen than agility + pistols or automatics) combined with a limit to your maximum number of spells at chargen keeps things fairly even. there's a high core cost combined with, for lack of a better way to describe it, a low cost for add-on modules, and in chargen with a fixed amount of available resources it isn't too big of a deal. but when you extend that out, the ability to quickly add on more and more modules means that your core, which was previously designed to be expensive enough to balance out those low-cost modules, can now be applied to far more modules, and the cost suddenly becomes comparatively a lot lower.