I can't really say I've had much of a problem holding threat as a PLD. There's the occasional problem with well-geared BRDs, as they like to start unloading the moment I start moving toward the boss. Other than that, though, I can't really complain. One good FB > SB > RoH combo and the boss is mine for good.

I always open with 2-3 Flashes before I start my combo. Maybe try that.