I think it still works. I have read wowhead comments from this patch talking about using this tactic but no solid confirmation that its still working. May as well give it a try since the other option is trying to kill the demigod lvl 90 guards.
Some tips for farming:
I found I made the most progress with this farming path.
Kill seahorn and the nearest npcs then go clear out the inn next to him. (make sure to kill the rouge in one of the bedrooms he’s playing dead.) Kill the goblin captain at the top of the inn, jump down and kill seahorn again. Kill the bankers then clear your way to the building with the pet vendors next to the mechanical rooster and kill them. Clear your way to the docks where the ship to the barrens usually lands then go up the ramp and kill the npcs in the buildings off to the side of the entrance next to the waterfall. Clear out the second floor and don’t forget to take out the herbing and tailoring npcs up the little ramp. Drop back down to the main level. (kill the firework vendors in the back if you want.) Then go back to master seahorn and repeat the lap all over again.
Try not to leave BB after you start farming. Sometimes leaving the town will make the lvl 90 guards start to bleed through into the phased quest. I think I was able to fix this by taking a flight path to bb and logging in and out just before I got there.
The bloodsail ships will have moved. The one that gives you the quests for each level of reputation you gain with them is parked over by the goblin statue now.
If a friend is in your group and within range they will still be effected by your rep gains/losses.
Other phased players can see you. Be nice and let them finish their quest.
P.S you probably know this but The Insane reputation requierments are not account wide. Meaning your toons can share the title but you have to fulfill all the rep requirements to earn the achievement on a single character..