I’ve described perhaps the biggest systemic problems, now for a few things relating to application of the rules.
These points aren’t as critical to game balance, but certainly detract from the game experience.
Preparation time and complexity, temporary changes, and figuring out just how powerful something is can all be problems.
Preparation Time and Complexity
Unless you stick to relatively simple scenarios, the time and effort required to prepare for a session is inordinate. It’s not too bad if you’re sticking to encounters consisting of a homogenous group of creatures and just need to roll hit points, but as soon as you start customizing or improving the monsters, or applying local effects the number of interactions and considerations can get big, fast. If you’re building NPCs you might have to watch carefully to make sure you don’t end up with a character that cannot be constructed within the rules. It’s easily possible, for example, to build a character that can’t have the selected feats because no slots were available at the time they would have had to be taken.
This affects players and PCs to a lesser extent, but is mitigated a little by most players having more time and focus to put on each character.
On the other hand, it gets ugly fast when temporary effects such as ability score damage (or buffing) is applied. A +4 bonus to Strength means a better attack bonus with most melee weapons, +2 damage (or +3 if you’re using a two-handed weapon – or possibly +7 if you take the +2 attack bonus and roll it straight into Power Attack), greater carrying capacity (which might affect movement rate), and +2 to several skill checks. Decreasing Wisdom penalizes a number of skill checks, reduces Cleric and Druid saving throw DCs, reduces Will saving throws, and so on. Remembering to apply these changes during play (and possibly just long enough for someone to cast restoration or to get hit with some more ability damage) and getting the changes correct each time.
Hit Dice vs. Challenge Rating vs. Level vs….
D&D 3.x tries at times to equate Hit Dice with something actually meaningful, but it is in fact often unrelated. For example, Turn Undead works on monster HD, leading to being unable to turn undead that are such low Challenge Rating they are no longer appropriate encounters, and Turn Resistance to prevent the trivial destruction of other undead that are appropriate encounters for the character level. Many spells affect target creatures based on their HD, regardless of whether or not they are suitable for the level.
This leaves out the entire mess of summoning, or playing monsters as PCs. This is related to the Level Adjustment point made yesterday, but I think goes beyond that.
The guidelines for building balanced encounters are somewhat misguided. They work okay if you’re within certain constraints, but it is easy to build an encounter that will obliterate a PC party despite looking sound on paper. Experienced DMs often have ways around these problems, but it is very easy for an inexperienced DM to get it wrong. This got somewhat better in the DMG 3.5, which points out some obvious hazards, but again it adds complication.
Ah yes. “CR Math”, many have come to loathe you. I don’t mind so much because I’m used to it and I’ve perverted it somewhat to make it simpler.
There are things that are poorly modeled in D&D that I’m not going to worry about here. In many cases they are a clear playability decision (such as six-second first aid), in others they are a handwave for things that seem useful to have but not critical to the game (Craft checks). In any case, they are less critical to me since they rarely come up in play.
I may have a third article soon on setting failures caused by reasonable application of the rules, such as the MagicMart down the street.