Loot mechanic including LD as I know it from over 2 years of raiding and handling loot permissions...

Player 1
Player 2/3 (Same account)

Player 1 & 2 engage boss, 3 is in group already and in position.
Player 2 does majority DPS and at 5% logs out via Alt-F4
Player 3 logs in and tags boss.
Boss dies.

Players 1 & 3 have loot rights, Player 2 may have loot rights IF he's still "online" when the boss dies, but thats a pretty small window.