I was dpsing orbonne the other day. We got LB3 at the last boss. I was all set to use it, but then like 4 people died to aoes, including a healer, so I held off because I just assumed the healer would use it to bring our group back without Weakness. But the healer didn't use it. Instead he started slowressing the co-healer, but that got interrupted by the maze mechanic (which we probably would have skipped if I'd used Lb3; he was on the edge of 15%.), and even when the healer made it to safety, he still didn't LB3, so at that point I just did it.
Saying this as someone who plays just about everything: it's annoying when a dps doesn't lb, but it's absolutely awful when a healer doesn't have it bound. Please ffs bind that shit and use it. Bringing back 4 people from the dead immediately without weakness debuff is such a boon to the group compared to saving it for a single hit that's gonna lob off like 3% at best.