Well, the thing as i said, with her normal skill, is that you need to be able to justify her hitting 5 targets at once. She fires faster with SAW meaning she will kill off the weaker ones faster as well, leaving her with only whatever stronger ones left to kill and those she will then kill faster. Chances that you get 5 enemies that need heavy magic damage and that also take a lot of time to kill, is rather small on most maps so her increased damage potential is generally a lot more valuable (i mean, with or without SAW she will just demolish the weaker mobs anyways).