I'm sorry but if you're losing threat to a dps, ESPECIALLY if its a target that you're both focusing on, the fault is entirely with you. It was not hard to keep threat before the buff but with the huge buff that SE gave to threat, this is inexcusable. This might only be excusable if you are SIGNIFICANTLY lower geared than him. Even against the high initial burst of Bards, you should not lose hate, unless the Bard starts attacking it before you even get there but even then, you have plenty of tools to get immediate aggro.

The question is: Should the DPS realize that you're a bad tank and back off? Maybe. I'm not trying to be an elitist and I won't kick or belittle you for being a bad tank but this is just fact. I know some of the newer PLD (WAR is inexcusable) have issues keeping AoE threat against BLMs but it is still more than doable. Also, a BLM taking hate for a few sec is okay, its not the end of the world.