Why wouldn't you always cast on the defensive?

[swrushing]

1) You could fail
2) You may not have maxed out your concentration, so you may not have a guarenteed success.
3) Your AC may be high enough that its better to take the AoO

Any ONE of the above 3 are valid reasons

Also add... the enemy's expected damage may be low enough to make it silly.

remember the CoD is 15+spell level while the "i got hit" is 10+spell level+damage... so if the damage expected is 5 or less, you are better off letting him swing... at least in terms of getting the spell off odds... this gets a little more of a expected results thing once you factor in "he might miss" as part of the odds of success.

Of course, there is the whole "even if i got the spell off i lost hit points" side of things, but only the whiners worry about that.

 

[swrushing]

I also don't like the mechanic for Defensive Casting, or Tumble for that matter - especially since once you get to around 9th level or so it becomes relativly pointless to check for either.

I fixed both by changing them to an opposed mechanic, based on the Attack modifier of the opponent. It's just not reasonable that a 9th level guy with maxed out concentration should have the exact same chance of successfully casting defensively when he's fighting a poodle with one leg with a 3 in each stat as he does when fighting a 3000-year-old, ancient+, fiendish, vampiric red dragon who qualifies to be a quasi-diety with a 50 in each stat.

I disagree.

here is why.

casting on the defensive and tumble are not COUNTERING the attack of the other guy. The prowess of the other guy has no bearing on this whatsoever.

How do i know this?

because the 3 legged poodle and the Vred ancient will both get one AoO. Their prowess has nothing to do with whether or not they get an AoO. Nothing they can do, beg, borrow, learn or buy can give them that swing.

Whether they get a swing or not is determined by ME. Do I or Do I NOT drop my guard? Thats what the AoO comes from. The VRED ancient monstrositydoes not get that swing because he is so much better a fighter than the paraplegic poodle.

he gets it because i let myself be distracted.

By choisng to cast on the defensive, i have decided I WILL NOT DROP MY GUARD. Even if i fail the roll, my guard never drops. I keep my attention on YOU and dont let you swing any more times than you normally can.

The roll is to see if I can ALSO, while doing that, get my spell off. Can i get my spell off while not taking my eyes off of you?

Thats not an opposed roll, at least to me.

Now, IF it were an opposed roll and you had to beat my roll by so much to get/earn an AoO so that whether or not you get a swing at all IS related to your prowess, that might make it sensible. But as long as the paraplegic poodle gets his AoO just as often as the VRED ancient beastie... its obvious prowess of the attacker is not in play here.

 

[dcollins]

Wasn't casting on the defensive an FRA in 3.0? If so, I am curious as to why they changed it.

No, it wasn't.

 

[smetzger]

Not really. If you couldn't fail (#1 is false), then #2 is also false, and #3 doesn't apply.

Yes really,
The original question did not specify that you couldn't fail. Merely for reasons why one wouldn't always cast on the defensive.

But if one couldn't fail a concentration check then their would be no reason to not cast on the defensive. Thats the benefit of pouring lots of skil points into concentration.

 

[Steverooo]

Casting Defensively is NEVER gauranteed! It doesn't matter if you have +20 on the roll!

A roll of 1 is always a fumble, on a task. Regardless of skill, regardless of natural ability. You always have a 5% chance to fail.

 

[Diirk]

I also don't like the mechanic for Defensive Casting, or Tumble for that matter - especially since once you get to around 9th level or so it becomes relativly pointless to check for either.

I fixed both by changing them to an opposed mechanic, based on the Attack modifier of the opponent. It's just not reasonable that a 9th level guy with maxed out concentration should have the exact same chance of successfully casting defensively when he's fighting a poodle with one leg with a 3 in each stat as he does when fighting a 3000-year-old, ancient+, fiendish, vampiric red dragon who qualifies to be a quasi-diety with a 50 in each stat. The mechanic as written was just silly. If losing the spell is based on what the other guy does (or can do), then the other guy should enter the equation at some point. It's like making a to-hit roll based around a set DC instead of the other guy's AC.

Fixed or broke? As a 9th level druid with minor buffs (bard song +1 hit, magic fang +1 hit, bulls strength +2 hit) in bear form my attack bonus is +17/+17/+12. So if I tried to cast defensively against myself with maxed concentration (12 ranks +4 con = 16), I'd have slightly less than a 50% chance on a level ONE spell. For a level 5 spell, you're looking at about 25% chance of success.

(Unless you take spell level out of the equation altogether? Making a level 9 spell exactly the same difficulty to cast as a level 1 spell?)

Regardless, sometimes you're just plain screwed regardless. If I roll 18 on the "potential" AoO, thats a DC 35 concentration check. Good luck.

 

[tburdett]

Casting Defensively is NEVER gauranteed! It doesn't matter if you have +20 on the roll!

A roll of 1 is always a fumble, on a task. Regardless of skill, regardless of natural ability. You always have a 5% chance to fail.

From the 3.5 SRD.

To make a skill check, roll 1d20 and add your character’s skill modifier for that skill. The skill modifier incorporates the character’s ranks in that skill and the ability modifier for that skill’s key ability, plus any other miscellaneous modifiers that may apply, including racial bonuses and armor check penalties. The higher the result, the better. Unlike with attack rolls and saving throws, a natural roll of 20 on the d20 is not an automatic success, and a natural roll of 1 is not an automatic failure.

 

[Al'Kelhar]

Fixed or broke? As a 9th level druid with minor buffs (bard song +1 hit, magic fang +1 hit, bulls strength +2 hit) in bear form my attack bonus is +17/+17/+12. So if I tried to cast defensively against myself with maxed concentration (12 ranks +4 con = 16), I'd have slightly less than a 50% chance on a level ONE spell. For a level 5 spell, you're looking at about 25% chance of success.

(Unless you take spell level out of the equation altogether? Making a level 9 spell exactly the same difficulty to cast as a level 1 spell?)

Indeed, that's what I do. The first Concentration check is simply representative of whether you are adept at avoiding (or withstanding without injury) the blow which is inevitably directed at you. Someone else pointed out that the Concentration check should be fixed, as it only represents the spell caster keeping an eye on an opponent while casting, i.e. multi-tasking. That's fine, but I use the first of two Concentration checks as a proxy for AC, not to represent whether you can multi-task. In fact, my rule is slightly more complex, in that you add any dodge bonus to your AC to your Concentration roll to give your total roll against which the attacker's attack roll is compared. I have a second Concentration roll which determines the consequences of a successful attack against the spellcaster, and spell level is factored into that. The process goes something like:

1. Spellcaster decides to cast a spell while threatened.

2. Attacker decides whether or not to use attack of opportunity on spellcaster.

3. If attacker decides to AoO the spellcaster, spellcaster rolls a modified Concentration check (d20 + Concentration skill + any dodge bonus to AC).

4. The spellcaster's AC against that AoO is the higher of the modified Concentration check and his normal AC.

5. The attacker rolls the attack roll for the AoO normally, and if he hits the spellcaster's AC as determined above, he hits the spellcaster.

6. If the attacker hits the spellcaster, the spellcaster must make a normal Concentration check in response (10 + spell level + damage suffered) or lose the spell.

In practice, this has worked out well and now my players are comfortable with it, it doesn't take much time out of combat.

Cheers, Al'Kelhar

 

[pawsplay]

Perhaps a feat (Stick with Opponent?) might be a suitable choice;

It's unnecessary. A fighter can always take a 5' step right back at ya and make a full attack. There is no way a cautious step back should trigger an AoO. An AoO means your guard is down, and that is not true when you take a step back. If the fighter chooses, he can keep coming at you. In some ways, the 5 foto step could be considered "Casting very defensively."

 

[Sir Whiskers]

Never mind - tburdett answered my question.