At that point I don't think tanks have any AoE specific taunts. Best they can do is throw on taunt stance and hope what few aoe moves they have generates enough threat. Were you guys using any crowd control moves? Makes pulls with larger amount of enemies much, much easier.
Biggest TOR fail I had was during the heroic in the Black Hole with three other people. We blow open the door to get to the boss and the two DPS (Sentinels) force leap at the boss before everyone is in and an energy shield pops up, keeping myself and the healer out of the fight. Had to sit there and watch them wipe lol.
Had that happen in Cademimu once on the final boss, except with Mara's instead of Sentinels. I healed the Jug tank and he soloed the boss at level 22. And I we couldn't rez the Mara's because the door didn't open, the general just ran through it and attacked us (we made them say "Mara's are not tanks, I am a dps not a tank" before we rezzed them