About rage points and backwards compatibility. A number of old effects/feats etc. state "increases the duration of barbarian rage by +1 round". How does this apply to rage points?
This is how we tackled the issue in our playtesting campaign.
The 3.5 barbarian gets to rage once for each four levels he has (plus the first level exception). The rage lasts 3 + (newly improved) constitution modifier rounds. Which is the same as 5 + (pre-rage) CON mod rounds. This is 5, 7, or 9 rounds for CON 10, 14, and 18 barbarians, respectively.
The Pathfinder barbarian gets 2 + CON mod rage points each level (first level is again an exception). We can compare this to 3.5 barbarian raging once per day. That is, we can compare rage points accumulated during four levels - 8 + four times CON mod. Or 8, 16, or 24 rage points for the CON 10, 14, and 18 barbarians above.
We noticed that the PF barbarians seem to get roughly two rage points per one round of raging under the old rules. Thus, we decided to convert "+1 round" to "+2 rage points per level".
Any flaws in this approach?