Revised Experience

Class abilities aren't the only things I want to strip down. I also want to strip experience and hit dice progressions for the six classes I've proposed down to two types: mundane and supernatural.

A mundane character needs 2,000 XP to add another six-sided hit die, doubling the required XP for each additional hit die up to 9 HD (but rounding the XP needed for 8 HD up to 130,000; 9 HD requires 260,000 XP.)

A supernatural character needs four times as much XP to add another six-sided die (8,000 XP for 2 HD, to 130,000 XP for 6 HD, with a suggested HD cap of 6.) When a supernatural character earns half the XP needed to gain another hit die, the character gains 1 hp of the next HD.

For either class, every additional 130,000 XP earned after reaching maximum HD earns extra hit points, not extra hit dice: +2 hp for mundane classes, +1 hp for supernatural classes. If you opt to go beyond the HD cap for either or both classes, you should continue doubling, instead of using a flat XP advancement.