Tried this in LFR last night, it's not really viable because each time you zone out and back in, though it does reset the loot timer, the timer is sped up exponentially each and every time. By the 3rd or 4th port back in, most of the raid was still there (and questioning why loot wasn't given out yet LOL) and the expiration on loot rolling was so fast I had maybe 5 seconds to roll need on the three items I was trying to win. As it appears that blizzard anticipated users abusing this and made it so each time the loot expiration diminishes faster and faster, I believe this is working as intended.
That being said I did win 1 of the items, the second item I lost, and the third I got passed up on because the loot timer expired too quickly. The item I won wasn't automatically given to me, I had to go back to the EoE and loot it myself. While I was there, I tried to loot the second item but obviously it didn't work even though the person who won it was no longer in the raid.
Hope this helps.