Recently my friend had mentioned that he was using a house rule for his players to calculate their hit point maximum, which I am both curious & hesitant to try with my players.
His way of determining hit points is (Str mod + Con mod + 4) per level, with a minimum of 1 per level (including first level). Apparently the minimum had to be added when a player purposely made a sickly character. Also, he said that the class isn't considered as those with larger Hit Dice are assumed to have more Strength.
From what I can see this makes characters too weak compared to RAW. Is my assessment correct?
He said he was trying to generalize hit points for the players, and allow strong wizards & weak fighters as options.
He allows them the choice to use either point-buy or to roll 3d6 for stats that they can then allocate how they want.
It might make you stronger or weaker, depending on your build
For finalized builds, it might make you stronger or weaker depending on how much Str you have. While leveling, your HP might go up slower than you'd normally expect at first, especially if you have a high HD, but it'll catch up once you increase your Str. (And you'll actually be able to prioritize maxing Str first as a melee fighter without losing out on HP gain.)
You'll also often be starting with even less HP than normal at first level, which might make surviving the first few levels extremely difficult.
Let's look at the two extremes:
A min/maxed Barbarian would normally have a +5 Con mod, a +5 Str mod and a d12. Under the normal rules and using averages, the Barbarian would get 7+5 = 12 HP per level. Under the new rules, the Barbarian would get 5+5+4 = 14 HP per level.
A min/maxed Wizard, assuming point buy, might have as low as a -1 Con mod and a -1 Str mod and a d6. Under the normal rules and using averages, the Wizard would get 4-1 = 3 HP per level. Using the new rules, the Wizard would get -1+-1+4 = 2 HP per level.
This might become more extreme in the case of rolled stats, where strength would often be your dump stat of choice, and a 4 in Str means you're essentially doomed to have 1 HP per level unless your Con can compensate.
It will benefit you if:
It will disadvantage you if:
Breaking even on levelup (assuming we use average HP):
If you are breaking even on a levelup, you still have less HP because your starting HP would normally be higher:
How quickly you will be able to compensate the lost starting HP depends on your Str. Determining when you truly break even if your Str is higher than required to break even per levelup, you'll need to divide your base HP difference by how much more Str bonus you have than required. For example, a Barbarian with 18 Str has 1 Str bonus more than required, so will break even in 5 levels and will be at an advantage after that.
A wizard with 14 Str has 2 Str bonus more than required, so will break even in 1 level and be at an advantage after that.
In short, if you do well or not depends on the chart above, if you have enough Str to break even, it makes no difference. If you have more Str, you're at a benefit. If you have less, you're at a disadvantage.
In addition, if you're able to get your hands on a Belt of Giant's Strength, you'll suddenly have a lot more HP.