Haven't been through all the new Heroics 5 mans but FoS was easy as far as I could tell.

25 man was a rather large disappointment to some in my guild but I expected it to be about what it was for us. We one shot all bosses and got the achieve for Deathbringer Saurfang. It took us about 2 hours after server stabilized and raid was formed to do it (god have mercy on my guild for having to listen to our raid leader's unforgiving and long boss explanations). We've had ToGC 25 on farm since October tho, so most of us were in 1/2 to almost full 258 gear so it was pretty easy to pull the numbers needed and coordinate well enough. Hopefully the next wings will be harder with more challenging content.