D'art has good skills but its not the best by far. Ambush (Gawain), Desertion (Asmund), Ressurect (Andromeda), and Soothing Breeze (Roland) are all skills I often use instead. Oh, and the affliction removal skill (Maiden's Prayer?) for Medusa/other status inflicting fights.

Also keep in mind that sniper shot overlaps with certain kamihime skills, so if you have someone like belphegor or cybele on your team sniper shot becomes a lot less valuable.