On Lost Valley maps, a lot of big terrain obstacles give no cover

I noticed that many huge rocks, tree trunks, and ruin debris give no cover though they look bigger than the characters. 

I see it often, but it was even more noticeable on the map for the Dominion ingredient hunting ...

I do not know how much work it would be, but they really look designed to give cover, so I suggest you add partial cover at least.