Is there a particular need for Rage to last longer as a class feature? By high levels you can probably expect the guy to last a minimum of 10 rounds (15 if he gets Lasting Rage or whatever that feat's name is). High-level combat doesn't usually LAST that long.
True. I just put that in when the barbarian would have gotten an extra rage per day to fill the gaps.
I still prefer my original idea of level times Con bonus. In the end you get a bigger pool, mostly, but it helps more against multiple attacks.
I'm just worried that it would go a bit nuts. I can see why 80 hp at 20th level isn't a lot, but that's just one change of many to bring the class up a single tier. I don't want to over-do it. I'm hoping the flat bonus at lower levels works well.
Here's the current progression, with ability descriptions:
1 Fast movement, illiteracy, rage 1/encounter, Rage (Temporary Hit Points)
2 Uncanny dodge
3 Rage (Mettle)
4 Rage (Fear Immune)
5 Improved uncanny dodge
6 Pounce
7 Damage reduction 1/-, Rage (Damage Reduction)
8 Rage (Haste, 1)
9 Temporary Hit Points (x3)
10 Damage reduction 2/-
11 Greater rage
12 Rage (Haste, 2)
13 Damage reduction 3/-
14 Indomitable will
15 Rage (Improved Mettle)
16 Damage reduction 4/-, Rage (Haste, 3)
17 Tireless rage
18 Temporary Hit Points (x3)
19 Damage reduction 5/-
20 Mighty rage, Rage (Haste, continuous)
Rage: Per the PHB with the following exceptions: the barbarian can use rage once per
encounter instead of per day. Instead of gaining a +4 bonus on Constitution, the barbarian instead gainst a +2 morale bonus on Fortitude saves.
The moral bonus to fortitude saves increases to +3 at 11th level when the barbarian gains Greater Rage and to +4 at 20th level when he gains Mighty Rage.
Rage (Temporary Hit Points): While raging, the barbarian gains a number of temporary hit points equal to double his class level. These temporary hit points
overlap with other temporary hit points and do not stack. For example, a 3rd level barbarian would gain 6 temporary hit points per round, but the total would never increase above 6.
At 9th level, the barbarian gains a number of temporary hit points equal to three times his class level per round. This increases to four times his class level at 18th level.
Uncanny Dodge: At 2nd level, the barbarian gains Uncanny Dodge, per the PHB.
Rage (Mettle): At 3rd level, the barbarian gains Mettle when he is raging.
Rage (Fear Immune): At 4th level, the barbarian is immune to fear while raging.
Improved Uncanny Dodge: At 5th level, the barbarian gains Improved Uncanny Dodge, per the PHB.
Pounce: At 6th level, the barbarian gains Pounce.
Damage Reduction: At 7th level, the barbarian gains Damage Reduction per the PHB.
Rage (Damage Reduction): At 7th level, the damage reduction granted from barbarian levels doubles while the barbarian is raging.
Rage (Haste): At 8th level, as a swift action the barbarian can gain the benifits of Haste for one round while raging. This ability does not stack with any other rage ability.
At 12th level, the barbarian can gain the effects of Haste for two rounds while raging, although it need not be two consecutive rounds. Each separate activation takes a swift action. At 16th level, the barbarian can gain the benifit of Haste for three rounds. At 20th level, the barbarian can gain the benifit as long as he likes.
Indomitable Will: At 14th level, the barbarian gains Indomitable Will, per the PHB.
Rage (Improved Mettle): At 15th level, when the barbarian is raging, he gains Improved Mettle. This works exactly like Mettle, except on a failed save, he only takes the partial effects instead of the full effects of the spell or ability.
Tireless Rage: At 17th level, the barbarian gains Tireless Rage, per the PHB.