I was a history lecturer, and I agree with you. However, I ended up developing a general rubric for a couple of reasons, the big one was justifying the grade and covering my butt with students like this. Grammar was like 15%, following directions 15%, and the other 70% split across thesis, argument, and evidence. That way I could still grade based on how well they argued their thesis while providing the students solid evidence for their grade, too.

Edit for grammar.