Killing the WKR isn't any better than not killing them in my experience. 9 hurkan kills and 5 yumcax, and all I have is useless grip/cape and bullet/ranged attack neck I'll never use.

Purely RNG loot in a battle system where the fights have huge entry costs, and generally take many hours is awesome, especially when useless items (grip/cape), are intentionally set as the highest drop rate items, just to dick players over in an attempt to keep them paying and playing.