Deathbringer's Will dropped last night and I won the bid. To re-count my previous choices when this happened, I am being pointed pretty strongly at a Marksman build.
So after the raid, I headed to Ironforge, flipped to my Pet-Tank BM spec and -BIG-GULP-re-spec'd it Marksman. I then queued for a random heroic while I worked out the details.
Well unfortunately, the heroic popped before I even had my pet-tank stuff off my bars, let alone having MM spells there. So I flipped to SV to just get it done.
The pug matching algorithm needs some help. I got slotted in with four people all from the same server who were in 2100-3900 gearscore gear. (I sit a little over 6k.) They all died on the first pull of Gundrak. I manage to kill off the last two mobs. On the first boss, the DK is doing quite literally nothing and something glibs the tank. As I'm waiting for them to ghost back in a second time, I pull out Flash, my Turtle and swap to my pet-tank gear. Flash is at around 33k health. Not crazy-good, but higher than the tank. And unfortunately, I could no longer go to my BM tank spec.
From that point on, things went smoothly. I continued to MD to the tank, but Flash OT'd one or two mobs. In my +stamina gear (I was around 44k health) I did a little under 60% of the damage.
So while this was a sad little pug, it made me realize that I don't have to give up pet tanking just because I'm giving up a talent allocation designed for it.