This has NOT been fixed. This may have been modified by Blizzard, but your chances of catching old crafty are still greatly increased while you have this quest. I discovered this recently because I do this fishing daily for both me and my wife's toon each time crocolisks in the city is the daily. My wife's toon caught old crafty on her first cast while having this quest. Sure, could be insane luck. But then my toon caught old crafty again within 3-5 casts while on this quest. Luck? I think not.
Furthermore, I referred this bug to one of my guildies, who picked up the quest and fished for about 30 minutes, again catching old crafty.
There is no way in hell a 0.1% chance results in the above catches. That being said, the quest does not increase the drop rate of old crafty to 30%. My guess is it increases your chances of catching old crafty to 1.0%.
Perhaps Blizzard intended to fix this bug by correcting the drop rate while on the quest, but incorrectly set the drop rate to 1.0% instead of 0.1%.
In any case, IMO this is not fixed. Your chances of catching old crafty still increase greatly while on the quest, crocolisks in the city.