I sent a petition to GM Albalfie of Burning Blade today regarding this quest. I had the same problem many of you were having. I went down to the depths of The Vile Reef, cleared about 3 murlocs -- (enough to activate the stone safely) and nothing happened.
The GM told me this was to be fixed in the next restart (Tuesday). As I was talking to the GM, I was running around STV doing quick quests. I decided to go back, (as hardheaded as I am) and try it again. This time it worked! I went down, killed 3 murlocs, activated stone, and there was Gazban! I hit him once, and started swimming to the surface for air. He followed me, but at one point he started casting, so I gouged him and continued my way up, he still followed. So there you have it.
The GM told me this was to be fixed in the next restart (Tuesday). As I was talking to the GM, I was running around STV doing quick quests. I decided to go back, (as hardheaded as I am) and try it again. This time it worked! I went down, killed 3 murlocs, activated stone, and there was Gazban! I hit him once, and started swimming to the surface for air. He followed me, but at one point he started casting, so I gouged him and continued my way up, he still followed. So there you have it.