Jax is not a good matchup for any fantasy D, so that bust can be somewhat explained.
Then at Denver in primetime with them doing better.
Two trap games without their best defensive (or all-around?) player.
I don't think they are a premier DST, but I think it's still hard to drop them though because they play the RB-less Chiefs week 15 then the Jets week 16, which are decent matchups if, say, TB isn't available.
Still, they'd have to show me something for me to use them again. I am benching them for AZ this week. I could still see them getting 3 or 4 turnovers and having a solid game though, except for the points allowed.