In beta, FD had a very high chance of working on equal cons. It becomes much less reliable the higher the mob is compared to your level. FD completely wipes your agro when successful.

AFAIK The only differences between the first and second versions were endurance costs and reuse times.

FD produces a message in the chat box letting you know whether your FD was successful. Unfortunantly a bug still exists when you have multiple mobs agro'd, FD will produce a successful message but because you have agro'd so many the game fails to drop them all from your agro list. Hopefully they'll be able to fix it.

been using FD pretty extensivly pulling in coterie infiniteum lately.

I can say that when the mobs was red, if i pulled a lot it felt like 50/50 weather it would work or i die :p

Now that mobs are yellow/white mostly it works so often i pretty much expect it to work on every pull, it must be about 90% success now
(note this is only against 4 dots, not tried 5's much)