Before attempting this mission, it is advisable to train up the team more than for the previous missions put together: Shadowboxer having Dark Vortex, Festus and Anya both equipped with Big Shield, Helena delaing more than 10 damage with Whirlwind and all teammates having above 36 hp would really help for the last battle of this mission. Having the Crimson Orb equipped or the Hero trained up to have Vengeance could come in very handy in the second part of this mission. Also you can always go back to the Mechanic's Base and fight again, to gain some extra money, or fight Vagrant in Somnus.