On that particular tactic, a lot of people are probably failing on one of the later moves. So, they get a few points, the tactic rating drops and the pass rate stays low. Kind of an artifact of tactics that have a partial solution that will still give you points.
I think at most rating levels, you will likely come across batches of tactics that are harder for you specifically. I have the same issue where I'll miss a string of tactics and have to slow myself down and work on getting my solve rate, and my rating, back up.
Two things are weird about the tactics trainer. First, there are tactics that are relatively difficult that don't get rated as more difficult. Take for instance tactic #273415 (posted below), 4819 attempts since Sept. 2016 have increased the rating from 1136 to 1212, and the success rating has increased by 0,2%. That strikes me as weird.
Why does it annoy me? Well, suppose I'm trying to get the tactic right instead of just trying to use as little time as possible. In most cases it leads to a steady increase in rating when I take my time, but with these puzzles I actually lose a lot of points. The opposite happens if I try to solve tactics fast, it'll cause my ratings to fluctuate more, but at least I get points for tactics like these, because I get most of the moves right.
The other thing are the really low-rated tactics (between 800 and 1000). As I joined the site, I did tactics without thinking much at all, and was only able to see mates and forks. When I realized I had to think harder about the problems though, I often also had to solve a bunch of really difficult tactics that I can't even solve today if you gave me half an hour to think about them. Getting back to 1000 was basically a matter of luck (i.e. not getting caught up in a cluster of super-tactics). Why does this happen?
Here's the tactic: