Iirc (been awhile), you can just redo the WP->down the road short stretch (towards umm…East Marsh?).
There is always a pack of Grobbles there. Kill then redo. It’s a lot of quick restarts (which you may not like). If you like doing East Marsh stuff (Sentinel), it’s on the way. There is also some other stuff that takes you by that section, on the way.
hardly, I was overkilling everything ten times over and one-shotting heroes.
If you check the toxic effigy grimtools, you’ll see there are no heroes for any version, and the higher-droprate “champions” (yellow trash) outright don’t spawn even though I meet the level requirements for them.
edit: I was able to spawn my first venomancer, so I was probably a little unlucky. Still, these guys don’t even spawn in every group. Farming this MI is an absolute pain.