Just curious as you say you are considering missing your attacks as a bug, what was your level when fighting the monsters on the left side of Luculla? They are level 14 so if you are several levels lower than that you will miss often, this is just general scaling.
The goblins are all around level 12 and its optimal to take that route first (story-wise aswell, hence why they are lower level, thus easier to subdue) - however you obviously can take the other, harder route if wanted and go to the mines later.
The death knights in the mines are meant to be sneaked by until you are able to fight them (again, story related).
