- Armor Class (AC) doesn't keep up with Base Attack Bonus (BAB). This means you need to keep spending money on better and better armor, or magic items to increase your DEX, or your AC. As long as the money comes in as expected, this is already "solved" I guess, but it strikes me as more of a clumsy patch than a really solid, robust solution.
- The CR system isn't just based on level, it's also based on the expectation of a number of magical "boosts". The higher up in level you go, the more ricketty and fragile this balance seems to be.
- Combat is too static, and not nearly "swashbucklery" enough. D&D rewards higher level striker type characters with multiple attacks per round if they stand in place, and the opportunity cost of not doing so is too high. Therefore, playing any fighter, barbarian, ranger, etc. type character who does something different, after about 5th or 6th level, is tactically very bad and maladaptive. This is, frankly, really boring, and not in harmony with what I believe are major literary and cinematic influences and source material for the game.
With me so far? Here's my solutions. The third one is new, but depending on what you've read of my gaming, they might all three be new to you as well.
- Most other d20 games other than D&D already have solved this: d20 Modern, d20 Star Wars, d20 World of Time, etc. If the expectation is not heavy armor or magic items, then a Defense bonus that increases as you go up in level, to simulate your character's fighting prowess increasing by getting harder to hit (not just by hitting harder) makes perfect sense. Luckily for me, the Unearthed Arcana houserule collection made this an easily applicable option for D&D as well, right here. You'll probably go over your wealth per level guidelines if you don't need to keep buying armor boosting abilities, but that seques nicely into my #2 solution...
- I don't pay any attention to wealth/level guidelines, and PCs in my games are almost certainly impoverished compared to what the designers assume. This means that they can't afford all kinds of razzmatazz magic that's at odds with the source material that inspired the game. Of course, this also means that I need to pay closer attention to what I throw at my players than others. CR becomes much more of a handwavey guideline rather than a component of a mathematical formula who's results you can usually count on. Of course, long-time players will remember the days before we had CR, when you had to do this anyway; know your party's capabilities and pick challenges that were appropriate for them based on that knowledge, not on some number in a formula. Guess what; we're back to that again. It's a key GMing skill that never should have been lost in the first place, in my opinion.
- Normally, per the rules, when your BAB reaches +6, you gain an extra attack (if you take a full attack option) at -5 from your first attack. This means that you don't actually move to +6, you actually move to +6/+1. For this houserule, instead of moving to +6/+1, you merely move to +6, but you gain the benefit of the Spring Attack feat for free, even if you don't have the prerequisites to do so. Similarly, when you would gain a third attack (+11/+6/+1), you instead only move to +11/Spring Attack but you also gain the benefit of Whirlwind Attack for free, even if you do not meet the prerequisites. There is no house rule for +16--no campaign I ever run will ever get that high in levels, I don't think (if I'm ever proven wrong, I'll come up with that houserule as needed.)
These changes will migrate any d20 based game into one that more closely mimics what I consider the key source material; fast, mobile, swashbuckly fight scenes between characters that rely on skill, not tons of armor and magic, to win their fights for them. I realize that there are some indirect consequences of this, though--I mentioned one in my solution #1 (which is largely offset by my solution #2 anyway), but solution #3 has several as well. First off, the average damage dealt by a hard hitting character may go down without the multiple attacks, prolonging fights and making them more dangerous. I haven't actually done the math, but I know this is at least partially offset by the lowered BAB on those subsequent attacks; you're not as likely to hit with them anyway. I could be wrong, and some playtesting should flush this out, but I don't think that'll be a significant enough problem to warrent "solving" though; it just means that combat flow and balance will be a little bit different.
Secondly, it means that the take rate for the feats Spring Attack and Whirlwind Attack (and possibly Dodge and Mobility, which aren't that useful on their own, but are kind of like tax feats that you have to pay before you get Spring Attack and Whirlwind Attack) will plummet and maybe even disappear altogether. I'm OK with that. I don't think that's a problem so much as just a... just a thing. It'll happen, but the game isn't any the worse for wear because of it.
Anyway, what do you think?