The DPS that wait until the last 2% of the bosses HP to hit the LB are probably my least liked types of players.
If your LB is going to do 4-6% of the bosses HP, use it when it has 7% left, not 1%.

This is why if I see a boss reach 5% or less without the LB used, I use it as tank.
The usefulness of the damage LB has already been squandered by that point.