1) Yes, ferocious bite is worth is on bleed immune bosses, providing you have low energy. If you were to take the talent, it would make it more worth it (especially if you have the 4t6 bonus). The only problem with this is, what do you drop from the rest of the talents? Assuming you take
this as the base build, where do you spend the 8 points? I would normally say natural shapeshifter, savage fury, brutal impact and one "free" point (probably in reflection, or maybe all of reflection or primal tenacity instead of brutal impact too). All these are optional, but I would say that, at a glance, savage fury will add more overall damage to your build than feral instincts, per point, even if you use ferocious bite every time. Most people won't take it just because it uses too many points for too slim a gain.
2) A warriors demo shout is about as powerful
at base level as fully improved demo roar (
proof - they get a rank of demo shout at 70 and we're left with the level 62 version). It's just not worth the point investment if you have one regular warrior, and that aspect is completely wasted if you have a warrior with improved demo shout in the raid.
3) No idea - someone else can answer it or you can try the PvP sub-forum.