Casting defensively with opposed check

[Xar]

If your magic user is casting a spell defensively the normal DC for the roll is 15+spell level. This seems a bit arbitrary to me, as a caster of about level 10 with a maxed out Concentration and the Combat Casting feat can let any of his spells off, even when threatened by a great red wyrm. Also, the Combat Casting feat becomes useless at high levels, as your spellcaster will have now sufficient ranks in Concentration.

I always thought of wizards as people who want to evade close combat at any cost, as it is very difficult to get a spell off when someone is trying to hack your head off. But around level 10 your spellcaster will be unimpressed by even the greatest dragon or the best fighter of the world. Sure, your enemies can try to grapple, but this isn't always an option, as it still takes too long to kill the caster, while you are vulnerable to his friends. Readying only leaves you with one attack.

So I came up with something different, a rule that is simple, elegant and realstic at the same time. If the spellcaster is being threatened and he is trying to cast defensively, the DC of the concentration check will be the AC the threatening enemy could hit if he would take his attack of opportunity. No more scenarios where the 20th level fighter has the same canche to disrupt you as a first level commoner.

Example: Merlin the 10 level wizard with a +18 on his Concentration is threatened by an orc. Of course, Merlin is trying to cast defensively. The orc now makes an attack to see how succesfull he is in trying to stop the mages spell. He rolls well, and can hit an AC of 21 with his attack. The DC for Merlin to cast his spell now becomes 21. Not that difficult, but Merlin can still lose it, so it would be better to avoid melee when possible.
Later, Merlin is attacked by a high-level fighter. He is now in deep trouble, as the fighter is an expert with his weapon, and can easily disrupt Merlins spells (he can create very high DC's). Standing toe-to-toe with him Merlin would be toast, which is much more realistic, and gives the fighter types an edge against spellcasters. With the original rules the high-level fighter would have no chanche to disrupt Merlins spells when casting defensively.

So any thoughts on this?

 

[hong]

Monte has a very similar house rule to this on his website. It's on the same page as his rule re Tumble checks, which have the same problem.

http://www.montecook.com/arch_dmonly5.html

 

[Elder-Basilisk]

There are a few other points to consider here.

1. Most wizards who end up in melee combat with an enemy are toast whether or not they can cast defensively. A 10th level wizard with a 10th level fighter in his face has a life expectancy of two rounds (if he's lucky) unless he does something about it (stoneskin, dimension door, phantasmal killer, etc).

It is currently possible (although difficult) to design a wizard for melee combat. (It usually involves multiclassing with fighter) Changing the casting defensively DCs will make this character concept harder even to pull off effectively.

2. The logic given in the PHB for the casting defensively the concentration check is that the character is able to cast the spell without letting his guard down. It would seem to refer to working up the magical energies to cast a spell in between thrusts, feints and parries. This is not something which is effected by the enemies skill any more than attacking with the melee weapons is.

3. It's also important to consider the way this interacts with other game rules.

The concentration check for casting defensively is a tradeoff with the concentration check for taking damage while casting (DC 10+damage taken+spell level--which combat casting doesn't help with). This is also mirrored by the concentration check to cast a spell while grappled (DC 20+spell level--spell may have no somatic components). If the DC for casting defensively is dramatically higher than the DC for taking damage, there's no point in doing it. If the DC for casting defensively is higher than the DC for casting while grappled, there's a logical problem. Any changes to the defensive casting DCs should take the other two DCs into account.

The proposed change will yield a situation that almost always makes the casting defensively check more difficult than the check for taking damage. Under the normal rules it's advantageous to take the AoO from weak creatures such as rats, xvarts, kobolds, goblins, etc. rather than cast defensively since they won't hit every time and even if they do, the DC 10+ (melee damage 1d6-1 or less)+spell level is easier to pull off than DC 15+spell level. The proposed change will extend this logic to tougher creatures as well. A troll, for instance, deals 1d6+6 damage on an AoO for an average of 9.5 points of damage if it hits. It's attack bonus is +9 so the average DC of the proposed casting defensively check is 19.5. On the other hand, if the wizard just eats the AoO, (5th level wizards will often have AC 18 or so (Mage armor, 14 dex, ring of protection +1, dodge feat or halfling). So, the wizard who chooses to take the AoO will have a 60% chance of having to make a DC 19.5+spell level concentration check. That's a slightly better deal than a 100% chance to make a DC 19.5 concentration check. Plus, the troll has used it's AoO for the round so if the spell is disrupted, the wizard takes no extra risk by moving 30 back and hiding behind another party member.

The proposed change (combat casting DC=spell level+attack roll) will usually yield a DC higher than that of being grappled by the time a wizard is 5th level or so. (A 4th level barbarian can be expected to have +11 (human) or +12 (half orc) to his attack rolls while raging. Even 4th level warriors will typically have +9 to hit).

4. This change will not just effect wizards. Clerics, sorcerors, bards, and druids, as well as high level paladins and rangers also quite regularly cast defensively. Making it more difficult for clerics to cast healing spells in melee range will make the game much more deadly in general.

5. The difficulty of automatically making concentration checks only arises when characters max out their concentration skill. That's a lot of skill points that could have been placed elsewhere. This is not too much of a problem for wizards but sorcerors, clerics, and druids often have to choose between having a decent concentration skill and ever qualifying for a prestige class. Personally, I think characters who choose to spend their time being good at concentration should benefit from that choice. I would expect that the effect of this rules change would be this:
Concentration, combat casting, and skill focus concentration would all become must have skills and feats for clerics who want to heal wounded comrades in the thick of battle. (This would probably have the incidental effect of greatly weakening the warrior cleric concept since it wouldn't have enough feats for things like power attack, cleave, weapon focus, and improved crit). Wizards and sorcerors would probably forget about putting any points into concentration and simply provoke an AoO by moving before beginning the spell.

In short, I don't think that the proposed house rule is a good idea (even if it bears Monte's signature).