It simply doesn't work properly.
Counter starts when the map appears on yoru screen. By the time your char actually spawns, it is already at 8-7 seconds. And because of the weird way RO2 handles buff counters when changing map, the counter on-screen might only start as the map loads, but server-side, it actually starts when the loading screen ends. This means that the buff disappears with 3-2 seconds remaining due to the client/server discrepancy (this also happens with other buffs in other maps).
Effective invincibility time = 5 seconds at best.
And even with the full 10 seconds, I'm not sure what it's meant to achieve. Group spawn camping a base, what do you do? Run aimlessly for 10 seconds? Do you think they will give up on you?
I would love some insight from other players about how they use this feature (and from CMs about how we could make it last more than 5 seconds).