D'art is not a good soul by himself. you only want to get D'art for ex skills (snatch and b-frame atk/def debuff) and gettin good ex skills should be low priority: get your backbone souls first, then go for ex skills. Other than that, its honestly up to you: if you'r not feeling like Andromeda's husband for life, then go for anyone other than D'art or Solomon. Arthur - consistent dps, Sieg - huge burst, Joan - good protection and excellent EX skills for other souls.