I just wanted to confirm a couple of things about the quest "Into The Deeps" to obtain Pebble.
Although you may look and do not see the quest on your realm, all is not lost. Currently I am 5/10 on the quest and 4 of those have been by realm hopping. I stand at the quest giver while I join various groups under Group Finder / Custom Groups. There are many folks that open their Garrisons for traders, Kura and other things that will give you a chance to look for a realm with the quest.
Every time I have found the quest, the group I was in was in raid mode. As you may or may not know, you cannot complete quest and get credit in a raid group. Not to worry, pick up the quest and leave the raid. It will take you back to your home realm. Even with the quest not being on your realm, it will allow you to complete it and turn it in on your realm, as if it was there all along.
Many folks have said they have been trying for months to get this done, I have completed 4 in 7 days. It did however take between 2-4 hours total per day to locate the quest, so it may be time consuming, but it is not impossible. Good luck to everyone who is after Pebble.