It's intentional that the higher powers are a bit lower in value. Many are one stage lower, in fact. A fighter would get a druid's defenderish power at 15 instead of 19. In exchange, the druid doesn't have to multiclass to get Strikerish powers too. It was the only way I could think to balance a hybrid class. Keeping powers one stage under doesn't make them so much as underpowered since those are still pretty good powers. And at the epic levels, they catch back up on the power curve with Wild Shape: Elemental, Eidolon, and chimera I think. Before I add power to them, I'd like to see them in play. Please, if you do get any in game feedback on their power level and it seems they're lagging badly, let me know.