Pally LB Invulnerability

[Gaiinahat]

Perhaps someone can explain to me how as a Pally I can have my LB invulnerability running and get instantly stunlocked and killed? I thought invulnerability was just that...invulnerability.

Before you ask, no the timer didn't expire, as soon as I launched it I was invulnerable, then I got stunlocked not even 3 seconds later, and gangbanged to death before the timer even ran out.