Guess it depends on what you mean by "outdo". Both mages or fighters/rangers that are min/maxed in a solo build can end every combat encounter in the game in the first turn, starting at around level 16, when 3 source point skills become available. Mages end up doing more overall damage (>100k crits easily on multiple targets), but that doesn't really matter since you don't need that much damage for any hostiles.