Do you use a LB at any other point? I'd like to think our group's DPS is pretty good (4-sometimes-3 meteors, 1 ghost, push last phase during 2nd heavensfall) and we have so far always had LB3 for dragon; at worst we hit LB3 during the first heavensfall "pulse" about 10s before dragon spawns. Our setup is PLD WAR(str OT) WHM SCH BRD BRD DRG BLM.

By virtue of the natural LB+ you get for just spending time in combat, it seems almost impossible that you don't hit LB3 by that point.