Melina there is a monstrous modifier in this game called dLVL, shorthand for "Level Difference". I'm presuming Hearing Voices is the Level 30 Black Mage quest, so- Level 40 or so, you're most probably going to annihilate them all in one hit, since you should be 5~ levels above the enemies.

Also, at level 50 all the quests aside from the L45 ones are soloable. The L45 ones are just plain impossible solo, though.