I noticed that sense RS 3 Gold came out, strange rocks are nearly impossible to get, I read on one of the other forums someone went 20 levels without getting a rock with it enabled, another person went over 1 Million exp without getting the second rock. I personally been trying to get my rocks and I only gotten 2…usually the first rock comes easy, and each one after slightly harder (or maybe its just a mental thing) but sense RS3 they are noticeably harder to get, the second rock even more so, the first rock is a pain, but obtainable, at least for the few I have collected so far..only 1 day a rock (playing 3-4 hours a day).
Of course I know that, the second rock is always harder to get, (didnt know the exact % or the math but I just know I done the sets 28 times), but right now for me at least the rocks have been abnormally hard to obtain it took me all day to get 1 woodcutting rock, which for me is usually the fastest rock.