D&D 5E Spell DC vs Magic User Attack Roll

[GMMichael]

They are spells that succeed every time. Therefore, no need to roll for it.

This is an interesting bit of D&D's flavor: spells always work. Much like the Warlock, though, this suggests that spellcasting is an easy thing that anyone can do. If that floats your boat, fine. However, I prefer the arcane to actually be arcane.

I probably said it before, and I'll say it again: if the magic user makes a roll, you have the potential for a spell to be virtually useless against -all targets-. "I rolled 3 on my magic attack roll. Bummer. I guess it's the goblin army's turn." D&D's designers prefer that a spell have some minimum level of success, and places the burden on the targets to decide the spell's degree of success - none, partial, full.

The question remains: having a base 8 or 10 spell DC is like taking 10 (or 8) on your magic user attack roll. Why not allow characters to take 10 whenever they want?

 

[pemerton]

I was thinking about this and it occurred to me D&D is consistent: the person with the chance of failure rolls.
You have a chance of missing so you roll, and you have a chance of dodging so you roll. The wizard or grenade thrower cannot "miss" so they do not need to roll.

A skill swordfighter can't "miss" either - the attack "misses" because the opponent successfully blocks with a shield, or parries, or dodges, or threatens to riposte, or . . . So why don't we resolve melee combat via saving throws?

 

[pemerton]

if the magic user makes a roll, you have the potential for a spell to be virtually useless against -all targets-. "I rolled 3 on my magic attack roll. Bummer. I guess it's the goblin army's turn."

You may not be aware that in 4e the caster rolls an attack against each target.

 

[machineelf]

This is an interesting bit of D&D's flavor: spells always work. Much like the Warlock, though, this suggests that spellcasting is an easy thing that anyone can do. If that floats your boat, fine.

I don't see it that way. I think spellcasting is a difficult thing to do, that's why not everyone can do it. A wizard has to train to become a wizard, and as he/she gains experience, their proficiency at it gets stronger. Just the fact that they can cast a specific spell is only because they trained to do it.

The question remains: having a base 8 or 10 spell DC is like taking 10 (or 8) on your magic user attack roll. Why not allow characters to take 10 whenever they want?

Do you see the armor class of, say, a fighter with AC 13 as a "take 13" every time he is trying to resist a sword strike or arrow attack? His AC is set, and is always that. He doesn't have to roll for it. That's the same concept as the magic user setting a DC.

With magic casters it's the reverse idea, yes, but still the same basic concept. And the reason why it's reversed makes sense to me. The DCs that are set are set for a reason. With certain spells when the magic user casts it, it automatically affects the target if the target is in range. There is no aiming at the target with certain kinds of magic, like there is with swinging a sword or pointing an arrow. But a magic spell that targets the will may be resisted if the target musters up enough will to do so. Younger magic casters are weaker and thus set lower DCs.

Maybe you don't think it makes sense to you, and that's fine. But I have no complaints, and actually like the way they did it. I don't want to have to aim my sleep spell. If the target is in range, I just cast it. If he can muster up enough will or whatever to resist it, then he does.

It creates this nice little system where if you have a very powerful high-level wizard casting a spell on a low level creature, the creature has a hard time resisting the spell, and that makes sense. If the wizard has to roll in order to see if he hits, then he might roll a natural 1 and completely fail at trying to cast the spell at a very weak low-level creature, and that doesn't make as much sense.

 

[pemerton]

With certain spells when the magic user casts it, it automatically affects the target if the target is in range. There is no aiming at the target with certain kinds of magic, like there is with swinging a sword or pointing an arrow. But a magic spell that targets the will may be resisted if the target musters up enough will to do so.

It would be very easy to model melee combat along these lines: a skilled warrior will always strike true, if the opponent doesn't muster up enough strength/skill/speed to deflect or avoid the blow.

If the wizard has to roll in order to see if he hits, then he might roll a natural 1 and completely fail at trying to cast the spell at a very weak low-level creature, and that doesn't make as much sense.

I don't see how it makes less sense than the weak low-level creature rolling a natural 20 and saving automatically.

 

[GMMichael]

A skill swordfighter can't "miss" either - the attack "misses" because the opponent successfully blocks with a shield, or parries, or dodges, or threatens to riposte, or . . . So why don't we resolve melee combat via saving throws?

Good question. I'll assume it's rhetorical, and add another:
Why should a skilled swordfighter have a 1 to 20 range of bonuses to add to his attack bonus?

You may not be aware that in 4e the caster rolls an attack against each target.

I am completely and blissfully unaware of most things in 4e.

I don't see it that way. I think spellcasting is a difficult thing to do, that's why not everyone can do it. A wizard has to train to become a wizard, and as he/she gains experience, their proficiency at it gets stronger.

You're right. Story-wise. But regarding the mechanics or rules, a player just says "I want to play a wizard," and poof! He can cast a bunch of spells, without fail. Also, it feels overlooked to me, but there's only one rule (3e) that prevents Joseph the farmer from casting Fireball. (INT limit)

My point was that something like spellcasting seems much more complicated than club-swinging, and therefore should require something (a roll?) to determine success.

Do you see the armor class of, say, a fighter with AC 13 as a "take 13" every time he is trying to resist a sword strike or arrow attack?

Actually, yes. The armor class rules assume that a PC always rolls 10 on his defense check.

It creates this nice little system where if you have a very powerful high-level wizard casting a spell on a low level creature, the creature has a hard time resisting the spell, and that makes sense. If the wizard has to roll in order to see if he hits, then he might roll a natural 1 and completely fail at trying to cast the spell at a very weak low-level creature, and that doesn't make as much sense.

You're right. Rolling 1s sucks. Here's how magic could work (but won't in 5e):

A high-level wizard casts a spell on multiple low-level creatures.
- Casting spells is a skill. So the wizard makes a cast spell check.
- The wizard can take 10 on his check if he wants to avoid a natural 1. Or 2. Or...
- The wizard's result is the spell DC.
- Avoiding spells is a skill. So the low-level creatures make spell-avoiding checks (saves).
- The low-level creatures can take 10 as well, if the GM thinks it's appropriate.

If the encounter isn't important, or the wizard is epic, or the GM wants to save time, or whatever, the GM can just take 10. The high-level caster succeeds, and well he should. If both sides take 10, but the caster's margin of success is small, the GM can decide that one or more creatures avoid the spell.

 

[Sadrik]

I don't mind if others want to play with opposed rolls. Just keep them way far away from me. The mechanics do not work. Most don't see that but they don't. The crux is bonuses play havoc. 1d20 roll vs. 1d20-1d20, or ranges of 1-20 in 5% packets vs. 0-39 in 2.5% packets which is a bell where deviation from 11 become more dramatic.

I will be removing all opposed rolls.

Here is the thing though. The two rolling methods do not work together but if you pick on and go with it throughout the system you are fine. Nothing gets weird if every d20 roll is d20+bonus vs. d20+bonus. Or the flip side d20+bonus vs. DC. Since most of the game is baked into d20 vs. DC, I am going to go with that and remove any instances of opposed rolls.

To my previous point in this thread, it is really a non-issue as to who should roll the dice. The math can work either way and it can be a table preference. I feel pretty confident saves as defense will be a rules module.

My concern with the rolling system is the chance of success. It appears too low. I think it should fall somewhere between 65% and 85% percent success. I don't see that in the system. It looks like 55% with an 18 stat vs a 10 stat. 35% if 18 vs 18. Advantage defender. Disadvantage game rules.

 

[Jester David]

A skill swordfighter can't "miss" either - the attack "misses" because the opponent successfully blocks with a shield, or parries, or dodges, or threatens to riposte, or . . . So why don't we resolve melee combat via saving throws?

I don't see a bullette parrying or dodging, or a beholder threatening riposte.

Yes, in the small percentage of times the mid to high level fighter is fighting another humanoid with a sword, maybe. But it's as much about overcoming the parrying, blocking, dodging, and ripostes of someone with equal skill, represented by their AC. It's just as easy to say that they hit the target but missed the small opening in their defense or the gap between their armour. It's not about hitting, it's about dealing damage.
As the skill of both comes into play, there's a contest between offense and defence. There could be failure on either part, with offense failing to take advantage of a gap or defence leaving an opening. However, for speed of play, we don't roll the opponent's AC every round. Which we could, substituting the 10 base AC for a d20.

The fighter is failing to bypass the defences of a skilled opponent. The wizard isn't failing to cast a spell or hit the immobile patch of ground with their fireball.

 

[Kinak]

You could easily make PC's CMD equal a d20 roll--instead of a static 10--plus or minus all the modifiers.

Yup, that's the plan. Then making monsters' CMB a static number.

The latest Hackmaster game has d20 rolls for every defense. It's nice when you roll high and avoid a high-damage attack. But it really sucks when your critical hit natural "20" misses, as has happened to me the past two game sessions.

Bummer!

I feel like opposed rolls don't add a lot to d20 unless there's a reason to conceal how well the player actually did. It just adds another step and makes modifiers feel less important.

Cheers!
Kinak

 

[Starfox]

The bell curve/opposed roll vs single-die linear roll isn't going to be solved any time soon. But the most important thing when deigning a game is what they do.

An opposed roll/multiple dire/bell curve roll creates a probability curve that heavily favors results in the middle. The net gain from a +1 bonus varies depending on where it is applied - it changes the probability a lot if the target number was in the middle, but only a little at the extremes.

A flat probability distribution, as with a single d20 against a fixed difficulty, has a static probability change with each +1 added (5% in the case of the d20). This is the same all along the probability spread, up 'till you need a 20 to succeed, then the curve has a discontinuity and suddenly flats out at 0% (or a static 5% if 20 is always a success).

The whole thing is made much more complex because the probability in itself is not always what you're interested in. For example, just as often the proportional increase is interesting, as in how much more damage will I take when a monster needs a 19 to hit me, as opposed to a 20? Edge effects like these is what 5E is trying to avoid with their bounded math.

Which is best? Well, that's what the discussion is about. Personally I prefer a pyramidal probability distribution, like what you get with when rolling 2 dice. I use 2 exploding d6 in my homebrew.