Currently the description for the talent Spellcraft, specifically the part about Spellshock, is rather incomplete:
You hone your spells to spellshock the targets (spellshocked target take a 20% damage resistance penality). Your spellpower is increased by X for purpose of determining spellshocks and your normal damaging spells can trigger spellshock.
As per discussion with DarkGod on how this talent actually works, I suggest the description be changed to this for better clarity:
You hone your damaging spells to spellshock their targets, if your spellpower exceeds the target's spell save. This talent gives a bonus of X to spellpower solely for the purposes of overcoming the target's spell save. Spellshocked targets suffer a temporary 20% penalty to damage resistances.