I finally got a chance to step away from work and scribble in my journal a bit. In an attempt to answer the questions which are still unanswered, I thought I'd attempt to resolve the hitpoints issue. As indicated in draft 3 of the design document, hitpoints are calculated purely by the Endurance stat. I could have made it more complicated, but I decided the less complexity in this area the better, at least for now.
Keep in mind, the emphasis of this little experiment is more about the creation of multiplayer games, and less on RPG's. So we'll often use the easiest calculations possible. At any rate...
Based on draft 3 of the design document, both the Tanks and the Handyman begin with 2 endurance, as for them that's one of the most important stats. After that they progress by 1 every level, except for 3, 6, 9, 12, and 15. On these levels they get +2 Endurance.
Although healers have the ability to...wait for it...heal themselves, they're still a vulnerable class, relying entirely on melee attacks and their ability to heal themselves effectively. As such, I decided to give them a little bit more health than Nukers. Specifically, they advance by +1 every level except for 3, 8, and 15...in which they advance by 2. Nukers advance by +1 endurance every level, except for level 15..when they get +2.
In addition to each class having slightly different endurance levels, a point of endurance matters differently for each class. Specifically, for every point of endurance a Tank receives 14 health; a handyman receives +12, a healer receives +10, and a Nuker receives +8. Here's a complete chart of endurance and hitpoints for simplicity.
The next topic we'll solve is Mana/Energy. This will function almost identically to Endurance/Hitpoints, but it will instead be Focus/Energy, and the advantages will be reversed, with Nukers and Healers having the largest bonuses. We could make it more complex, but there's an inherent beauty in the symmetry and opposite nature of Health and Energy.
Now that we've got an idea of the scale of hit points and energy, we can create our combat rules with the above assumptions in mind. This is one advantage to having hitpoints and energy pre-determined by level. It makes game balance much easier, as we don't have to worry about a level 5 Nuker having more health than a level 15 Tank, just because they poured all their ability points into endurance rather than focus like they should have.