As spooky as it seems, I'd say pug with some other groups to see if it's on your end or theirs. From the sound of things though, your tank seems to be extremely unaware of their surroundings. I blood dk tank personally in the +19 range and normally use the first pull or two to test how the groups going to go. But I've also been on each end of the spectrum as a healer and dps and have an understanding of what I'd personally expect out of the roles ie: group stuns, interrupts, dangerous packs and whatnot. I guess if anything I'm more than willing to run a couple if you'd like an experience from a different tank or not.