I did first few bosses of tfb hm with guild with a mix of old high end 50 pve and some new 55 gear. We found first 2 bosses really straight foward but some trash specifically cores a bit harder then before (the section with 2 cores esp was really troublesome). Also the puzzle boss had significantly more trash and we had some trouble with that one and got bored so gave up
(pvp guild xD) I would say its not difficult at all.
Also we did first 3 bosses on S&V hm and i wouldnt say gear requirement is as high as you'd think once you get mechanics down again i was in worse gear when we did that then in tfb (had less 55 gear..) Few of us where in pvp gear.. (we also did 4 melee deeps.. crazyness xD)