Thrundarr quest monster is level dependent. If you're level 50, he might ask you to kill a greater moloch.

You can also encounter herds of rust monsters in the wilderness.

I agree that the current type of monsters asked for in the first quest is probably too rare, making it more difficult than the second quest. If the second quest is venturing beyond AF, it doesn't make much sense that the first quest routinely requires players to go to much more dangerous places than the AF, like the TotHK cavernous levels.

At the moment you will most likely get a monster that spawns below DT, even if you ask him at level 6. See this test.