Hasnt not much to do with new players. It's most of the time just lazyness by some peoples part -> Somebody else will do it. Still happens at lv70. And some wait for the Tank to scream LB, which isnt a good idea at all. I saw many many many deads because of the last option, bec of some fight 1 shot 1 kill mechs.

As a melee myself I use it right away at the boss when it's full. But only if the party is good or else you have a wasted LB + wipe.