Quote: Jason Bulmahn
"Skills: Concentration is gone and its role got shifted to Spellcraft, which has been pointed out as unfair to some classes that do not invest in a high Int. One compromise that is being considered is shifting the entire raft of uses over to a Will save, removing it from the skill system entirely. Thoughts?"
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Jason,
Why not go ahead and remove “casting defensively” from the skill system entirely, but as an ability check instead of a saving throw?
If a caster is being threatened and wants to cast a spell without dropping his guard and provoking an attack of opportunity, he would need to make a successful ability check using whichever ability is tied to that character’s spellcasting. A wizard would use his Intelligence. A paladin would use her charisma. Etc.
As originally written, the DC to cast defensively ranges from 10 to 19 (10+spell level). Assuming a caster had the bare minimum ability score required to cast a particular spell, he would have to roll anywhere from a 10 (for an apprentice with a 10 Intelligence casting a cantrip) to a 15 (for a high priest with a 19 Wisdom trying to invoke a Miracle) on a single d20 to successfully maintain the proper mental (or spiritual) focus to dodge and weave and still cast his spell.
Even in the above example, the marginally talented apprentice has a 50/50 shot to handle the pressure well enough to daze the threatening goblin, while the high priest has a challenging but not impossible roll to make. Both characters are using the most powerful spell in their repertoire under rather intense pressure to perform.
Higher level characters still have an advantage over lower level characters, as higher level characters have more of an opportunity to permanently or temporarily raise the necessary ability score (and plenty of other incentive to do so). Non-major spellcasters such as Paladins and Rangers are less likely to raise their spellcasting attribute, but they also cap out at 4th level spells (DC 14) so casting even their most powerful spells defensively in combat should stay fairly easy for them.
Characters are encouraged to cast their spells in situations where they are not directly threatened, but if the difficulties never rise so high as to become impossible if they are. This would also give the Combat Casting feat a little more mileage.
Thoughts?
-Jason