Thing to consider too when deciding who to have use the Lb. Some classes, monk springs to mind, have to keep stacks up, so using a Lb locks them in animation long enough for them to lose their stacks.
Talking about animation lock, it can be even dangerous to use Lb at an unfortunate time. The time you cannot move after using it is rather long and if you get hit by a mechanic during that time, you'll most likely get killed (talking savage here, in all other content it honestly doesn't matter when it's used or if you eat an aoe because of it).