Cat Claws isn't that good. Dragonhron Lance will be useful once Dragon-type enemy raid event is added to the game.
Anyway, just collect enough recipes and scrolls.
Bloody Bone is weak to Strike and Earth attack. Use Mont Leonis's Body Slam or Etre's ability to deal over 2000 damage.
You can complete the mission by dealing 1,000 damage to 2 enemies (or 700 damage to 3 enemies) at once as well.
Use AoE abilities like Mediena's Cosmo Plume, Gilgamesh's Kotetsu, and Mont's Destiny Cross (Limit Burst) to deal damage to multiple enemies simultaneously.
AOE Evocation Magics should work fine as well.
UR Units & Tier List
Upcoming Unit/Vision Card Release Schedule
Mont the King of Leonis
Helena (Black Witch)
EX Job Guide