You can always get a guaranteed legendady from the jabber mogwai. If you kill him with a fire weapon he drops the hellfire. The hellfire isn’t great, but it’s something.
Also using a cryo weapon you can continuously spawn in mogwais and farm them for hours, but they may have nerfed their xp so try offline.
I am not sure on the name, but that sounds familiar. All I know is you get sent to blow up a poop damn that is preventing Homestead from getting its water. Yes complete the Side Mission and turn it in. Return to the Save Point just outside the fence leading to the area with the poop damn. Quit and Reload the game, run that mob and mini-boss. Wash, Rinse, Repeat. I ran that area over and over since it was the shortest distance to a “mob + mini-boss” and scored a lot of XP to finish getting to 50 by myself.