This is doable with the following classes confirmed.
Rogue - Blind big guy kill lowbies aND VANISH (2 min down time)
Mage - Slow big guy kill lowbies and invis (3 min down timw)
Hunter - Misdirect to pet, trap big guy, kill lowbies, dismiss pet, fiegn death (downtime is as quick as you can reset the mobs) **fastest**
i have heard that Night Elf shadowmeld doesn't work from some and i hear here from others it does...so i can't confirm. Invis pots do NOT work as you have to be out of combat to pop one.
getting to the correct spot can be done on any class however without an ability to put the mobs into EVADE you will die once and not be able to profit much off this exploit. However that said while dead you still gain reputation. so if you know someone who can do this and just want the rep grind to 5999/6000 friendly i suggest going in there and dieing and afking while they farm.
There was a loot drop nerf put in place last night. The nerf effects all all trash mobs in firelands as far as i can tell. Yesterday (pre-nerf) we were getting an epic literally every 5th kill. Today you are lucky to get one in 100 kills. I can confirm this same thing has happened to the trash run raids i know that have been running since tuesday. Epics still do drop though, gold to be made from just rep farming is roughly 1.5-2.5k an hour.
If you are doing this with rogues you can do constant pulls by having one rogue stealth while the other rogue pulls then switch while the first rogues blind CD reset's. i know a few people doing this and they manage to farm much faster than i can solo on my hunter.
hope this info helps someone and stops all the repeat questions.
-DeMoN