In tough fight lb3 usually saved for healer and to certain situation, tank. Dps probably the least lb3 user in big fight like omega or (currently) susano extreme because how easy things went from "everything is fine" to fubar in less than 20 seconds.

i see some dps didnt use lb usually because they are still in the middle of their rotation something like "on fire" moment. And then certain class is more akin to use lb3 like bard who generally has very minimal rotation, or someone who broke their chain combo.