You need to do a lot more reading before you venture into even the Simple Questions threads.
Actually two questions:
1. When I hit a Mob, particularly a boss, with Froststrike, they sometimes resist the Damage partially (mostly 25%, I think). Since this is a severe DPS loss, is there any way to prevent this from happening? Do I need spell penetration (if so, is it reasonable to go for it in PvE content?)? Do I need to be beyond the melee hit cap of 8%, or is the damage even related to the spell hit cap?
2. With 3.2 coming up, is it reasonable to aim for a +melee hit chance around 20% or is this just overshooting things? I guess +hit plays a bigger role in this build, the question I'm asking myself, however, is, if it's that important that I want it, even if I'm already at 10% hit or so.