I have used them 12 times, with a 6-6 win/loss ratio.
They require a changing of tactics, and entirely different play style. Gone is the rush and bash style. You really have to be selective about how you apply your charges, in what order, and where models are placed. I have also seen a bit of a reduction in people using heavy anti-tank weapons (meltas, lascannons, etc) and that lends a bit of survivability for our MCs.
I'm just going to plug in here that IMO, Biomancy is the only discipline worth taking. Iron Arm is worth its weight in gold, and giving FnP and Regen to guys is great too. Really most all those powers are good. I found that I actually had a bit more psychic ability in a 2k game then I was used to using, capping at 8 psychers all with biomancy in use.
So no, not dead. In trouble, I wouldn't say that either. Simply challenging, but still very doable.