Is maximum PC hit points going to unbalance the game?

Question

I don't like randomization in character creation/advancement, so my preference is to not roll for hit points, but to take a fixed value every level. PCGen gives me several options, and Pathfinder Society uses +median(dX)+1, so clearly fixed HP isn't an issue.

I'm considering using +max(dX) HP every level. (If a class normally gains +d6 HP per level, the character gains a full +6 HP every level.)

1. Does this have an undesirable effect on game balance and combat down the road? For fighter, this means (base) 100 HP at 10th level instead of 50 HP, which is significant.
2. Does it make a difference if my goal is creating a buffer for a very small adventuring party? (Just two players, but I want to use published adventures without stripping down the encounters too much.)
3. Is this a poor option to compensate for small party size? (If so, don't give alternatives here. I'll ask another question, if there isn't one already.)

Answer 1

It does not cause any issues. My group does max HP as our default setup.

The only difference is removing an element of random from the table which most people are in favor for when it comes to mundane but important elements like HP. It removes the "flavor" added by being bound by the dice constraints so it is unlikely that 2 lvl3 fighters with the same CON mod have the same HP.

Just don't forget its class hit die PLUS constitution mod PLUS favored class (if applicable) each level up

Answer 2

No, it's not inherently unbalancing. In fact the lead answer in How to mitigate glass cannon syndrome in Pathfinder? recommends it as a way to reduce rocket-tag syndrome for damage-dealing with the downside that combats take a lot longer and can drag.

It's a decent way to "toughen up" a 2-PC party though it won't help against the probably more difficult issue of failing save-or-dies, so I would augment it with a hero point kind of mechanic to allow rerolls as well.

Answer 3

It isn't going to unbalance the game, but there is a small change to mathematical balance between classes. The change will very slightly favour non-spellcasting classes, for example the expected ratio between d12/d4 when rolled is 2.6, whilst at maximum values it is 3.0 - Barbarians will be slightly more robust compared to Wizards under the default rules.

Now non-spellcasters are not generally balanced against full casters very well in Pathfinder anyway. What this change might do is move the "sweet spot" where it all sort-of works up by perhaps some fractional level. It would not be a worry, most likely you won't notice.

One thing you probably should do to go along with your change is to increase value of healing effects. Otherwise more spells and resting time will be used by PCs healing themselves back up. If your goal is to make the players survive more and feel their characters are more robust, then it would be reduced if they use up all their cleric spells on healing and had to rest longer between adventuring days. I'd suggest something simple to track such as healing effects that use d12s instead of d8s. Maybe double the rate of natural healing too.