Casting on Defensive...too easy?

[Diirk]

we use a varient of 15 + spell level + Bab of threatening enemy. It works pretty well.

Since not many bad guys have a real high bab but get most of their ability to hit from strength it works out pretty well.

So lets take a 10th level wizard, he can cast 5th level spells so core rules would put casting defensively at dc 20. This wizard will most likely have 13 ranks in concentration and +2 from con. Combat casting isn't a very usual feat to take, so I'll ignore it for now. So said 10th caster has to roll 5 or more to cast a spell defensively. Ok.

Now under your system, lets take a CR 10 monster... say a fire giant. BAB of +11, so to combat cast a 5th level spell, its dc 31. With a +15 concentration skill. Now he has to roll 16 or higher.

See a problem? Even with combat casting he has to roll 12 or higher...

How about an efreeti? CR 8 with BAB of +10. Still DC 30. Clay golem is CR 10 and only has a BAB of 8.. so thats "only" a DC 28 check. Great, a 10th wizard with maxed out skill ranks and a feat investment can cast a 5th level slightly over half the time.

Maybe this problem gets better as you go up in levels? Lets see.. a 20th level wizard casting 9th level spells (15+9 = DC 24 in core). 23 skill ranks in concentration, +2 con, lets give him combat casting to be nice. So +27 concentration check.

What do we fight at lvl 20? hmm, lets see... how about an old red dragon? cr 20, perfect. +28 BAB so you're looking at a DC 52 concentration check. So we need to roll a 25 on a d20. The tarrasque is CR 20 as well but I wouldn't want to be making a dc 72 concentration check at level 20...

Even if you take something as puny as a Rakshasa with 10 sorceror levels, (BAB of only 12 ! at CR20), you still need to roll a 9 or more to cast a 9th level spell.... WITH a feat spent. I can't even begin to say how wrong I feel this houserule is.

 

[molonel]

Concentration checks for casting on the defensive are designed to be automatic at mid- and higher levels. In order to maintain that proficiency, characters have to burn a skill point on a skill designed solely to allow them to use their own class-granted abilities. Casters, especially wizards, already take it in the shorts to use their abilities. Creating some weird BAB-based DC check narfs most spellcasters, especially arcane-types, beyond all logical comprehension. A high-level caster casts a spell, probably on the defensive, with a medium- to high chance of failure, then he probably has to roll a caster level check for SR, then the target rolls a saving throw.

 

[Ridley's Cohort]

Actually those houserules are particularly harsh on Sorcerors; the typical Wizard has twice as many skill points to work with as a typical Sorceror. Even after maximizing Spellcraft (in order to learn new spells) the Wizard can maximize Concentration and still have more skill points to play with than the Sorceror.

Succeeding progressively more easily at things that were once tough is the entire point of the level based system. Otherwise we would just stay level 1 and make a career fighting kobolds.

 

[FireLance]

5-foot step + cast spell usually means no need to cast defensively.

In extremis, move + cast spell attracts an AOO, but you can usually cast safely.

I don't see a problem with automatically suceeding at casting on the defensive.

 

[Ulorian - Agent of Chaos]

Wow! I used to agree with the original poster's viewpoint, but after reading some of the posts in this thread, I'm convinced otherwise. Thanks wilder_jw, Thanee, Spatula, and Ridley's Cohort.

 

[Kabol]

5-foot step + cast spell usually means no need to cast defensively

Just add a Creature with Reach - which is Most higher lvl mosters as i have seen - and 5' step is not an option, As you still within threatend range