Some easy farm info:
1. Set a campfire.
2. Park trackbot on hill (behind balcony).
3. Kill all 4 castle named (GV, RM, XS, TA).
4. If HG spawns: kill him, get Vald
5. If HG don't spawn, go somewhere else, kill stuff, afk/websurf, whatever.
6. 1-2hr check respawn w/trackbot, repeat.
I got normal HG/Vald 2x (back to back!) and later that night, Fabled HG/Fabled Vald in one swoop. HG is tied to the death of the namers in castle (at least XS, TA for sure). Kill em. he spawns, cool. he dont, try named again in an hour or two. Dont waste time killin the trash all day (or the Corrupter, insatiate :P)