Tank was overreacting and you can tell them to touch grass. Generally speaking you get a feel for the run and if it's say an 8 man or a 24 man where people are dropping dead and you have lb3, maybe save that for the healer until you reach single digits on the run and even then keep watch for mechanics, otherwise, pop it.

If you see the boss dropping and you won't get to lb2, hit that lb1, and if you have an lb2 fired up, pop it off. I'll throw an lb generally speaking when I have a clear moment to do it, even if it's at say 40% if I see the boss dropping fast. If a tank saying anything I'll ask him if he needs some new friends or if he hasn't had a chance to speak today yet, pay them no mind.