I highlighted your questions in red but I wanted to add extra details, I'm sorry I'm copy and pasting but there's no other way to explain than the facts.
March 26, 2012 Further Spring Patch Features
If the server identifies that your connection is gone, the time it takes until your character is logged out will then depend on your vocation because each of them has different chances of survival. Druids and sorcerers will be kicked out of the game after 40 seconds, paladins after 50 seconds, knights and characters without a vocation after 60 seconds.
Also, if the server identifies a connection loss, your character will be ignored by monsters for 30 seconds. If your connection gets restored during this time, monsters will attack you again immediately. If you cannot reestablish your connection and your character is logged out so that you have to log in again, a new login mechanism will help to give your character a certain chance to survive such a complete kick.
In general, from the spring patch on, a character will be ignored by monsters for 10 seconds upon login. However, the already existing delay of 10 seconds for area attacks and PvP attacks will be extended to all aggressive actions. So you will have some time to orient yourself but in which you cannot fight. As soon as you move your character or the 10 seconds are up, monsters will stop ignoring you. Please note that if you close your client in case of a connection loss but your character is not yet logged out while you try to log in again, this measure will only be effective twice in a row.
Last but not least, a special icon in the client will be displayed if the quality of your connection falls below a certain threshold and seems to be laggy. If the client does not get any response from the server anymore, you will also be informed about it with a special icon.
Post by Mirade
There is also another game mechanism which will help in case of a kick. If a monster does not have a target anymore it will try to walk back to its original spawn so if you lure monsters away from their monster homes when hunting and you lose your connection. This means monsters will not only ignore you for a certain time but also start walking back to their spawns (if there's no other target near you) which should also help to increase your chance of survival.
Generally speaking, though, hunting always poses a certain risk of death. A full protection in case of a connection loss would make this feature more attractive for abuse (players forcing a disconnect). Instead of being a feature to alleviate the negative impact of lag and kicks it would become a feature to escape tricky situations - and it is simply not meant as such.
As some brought up, area affects may hurt a disconnected player even if the monsters are ignoring them due to another player in their vicinity. As I understood it, the player would be invulnerable to damage from monsters during this time. Could you clarify this? No, a player does not become invulnerable. You'll just be ignored by monsters which means they won't target you. But you will still take damage from area affects.
If players are invulnerable to damage during this time, it is essential that creatures are able to move through the disconnected players. As I just said, players won't be invulnerable. Also, monsters cannot walk through them so a disconnected player still "blocks" the way for monsters.
I hope also that players get teleported to their home temples if they are in certain areas such as the Zao arena and suffer a kick. It might be a way to circumvent the system to only allow 2 players at a time in the arena. No-logout zones will continue to work as they already do in case you get kicked there.
Concerning PZ lock and battle sign: The protection mechanism (ignored by monsters for 30 seconds, kick after 40/50/60 seconds) will not work if you kill another player, get a pz-block and lose your connection. In that case nothing will change to how it is currently handled: your char will be kicked after 15 minutes.