I may have worded my last reply a bit erroneously. "Everyone" having more HP applied only to those with class levels (PCs and NPCs alike, but not monsters with only racial HD).
The way the system is set up now (which I'll unveil fully in Patch 1.2!) is that taking a class level gives you a certain amount of bonus HP, and NPCs can be set by the DM to either have that bonus HP or to have a lesser amount - whether they take a PC Class or an NPC Class isn't tied to that. It's tied to each level - class or racial HD?
There isn't one "you have a class!" lump sum of bonus HP. If, for instance, a Bugbear takes a level as Rogue, it would have the bonus HP for that level. I'm hoping that it works out to be a useful tool for DMs to customize: do I want this NPC to be minor or significant? If it doesn't work out, I'll revise the system and see what I can do to improve it. But it's intended to give the DM a few more dials to use: does this NPC have an NPC class or a PC class?; do I give this NPC the full bonus or the reduced bonus? With the system you can have NPC Wizards that are - at least in one aspect, HP - objectively weaker than the PCs. The same goes for other classes, of course.
Alright, fair enough. Generally monsters will have more HP anyway.
I'm a lot less concerned with giving boosts to monsters. While I want T5 to have some degree of realism and to have a lot of options for high-tension, dramatic adventures and combats, if Team PC can regularly drop racial-HD kobolds in one hit at level 1, I'm not too worried about that. Maybe it means pulling back a little for Team PC if enemies can't even land a hit before they die, or maybe I push Team Monster up just a tiny notch, but I don't intend to make monsters a whole lot harder.
In my experience, while PCs do need a statistical advantage, you can always compensate for monster power with poor tactics, which is why I tend to do the opposite: Bump up the numbers, especially for dumb monsters, and play stupid. Generally, the best fights are those where the players start out thinking No-Fair, but then pull through.
Now, enemies with class levels will be a bit more challenging, but hopefully the HP system makes it so that Team PC is always clearly extraordinary in some fashion - that boost is what makes them the heroes of the game/story/world.
I tried to do this via Gestalt/no gestalt. In this E6 game there were the elite casts, so to speak, which had either T1 PC classes or some sort of Gestalt, then there was the trained group, ranging from PC classes without gestalt to to NPC classes at the low end, and finally commoners - even those with up to three levels by default. Monsters were different, they had no gestalt, but compensated with inflated ability scores.
The reason for this is that Gestalt often just gives more options where just giving numerical boosts is more boring, and can also have greater problems. Of course, the Tier system gestalt can actually go the other way, there, because what you produce is often just any odd class gestalted with Warrior, which means full BAB.
Now, there might be a rare enemy that has that same degree of skill - class levels, full HP boost - but that's not mandatory. That's an option for the DM. If the DM wants the Evil Wizard to be really competitive, they won't use an NPC class to be "close enough"; they'll use the actual Wizard class, and they'll give her the full HP bonus, and maybe the Evil Wizard will even be max level with a few bonus feats past 5th.
Do understand that all a HP boost does for enemies is actually make the lower tier classes WEAKER. HP boosts without save boosts means that melee can go packing and anyone with BFC or SoDs will rule the world. Now while optimised melee can be every bit as bad as wizards playing rocket-tag, this is just something to watch out for.
You might want to consider looking at the 4th Ed save mechanic: Making spells roll vs Save AC is generally a more balanced mechanic. At these low levels the numbers should all still come out approximately right.
Save AC should be 10+save bonus+ ability mod+other mods; Spell attack roll should be 1d20+spell level +ability mod+other mods. A spell that has no save now might still always hit. Rays stay the same, attack with Dex and target touch AC as before. Only rays with additional saves create problems, which might be alleviated with two attack rolls or attacking the higher of either Touch or Save AC.
Depending on the results of this, maybe change the spells/day or the bonus spells/day table.
Damn now I'm talking about this so much I want to play this old E6 game again
. And I have neither a group nor time to run it, really.