That is almost guaranteed to be a complaint against the tank losing aggro rather than a compliment to you. I would assume that they had a better weapon/gear, or were otherwise expected to generate more threat (WAR stacking STR comes to mind) but were not.
So far, in my tanking experience, things have been pretty chill outside of leveling dungeons. Then again, I also have the benefits of being a high 120 ilvl DPS main and was sitting at 114 on my WAR once I hit 50 because I built up the gear over the last six months or so. Additionally, one of my best friends in game is a PLD main and he's been fantastic at covering tank mechanics I wasn't aware of when we've run stuff together.