Blood Hunger procs provide a 1s non-stacking Heal buff, based on % HP. Honestly, with how much this class crits, the heal duration is largely irrelevant. The increase per level is extremely low, although the first level gives you 5% (? I think it is 5%), and subsequent levels add 0.5%. Perhaps it could scale more linearly to begin with.
I think the main purpose of leveling Rage Retaliation is to get to the Lv15, where there is no cooldown on the skill at all. I think this ends up being a skill where either 1 or 15 points are invested in it. Not too sure what could be done to fix this. (P.S.: If I recall correctly, this also only works at melee range)
Frenzy Mastery could even be left at 0 points, because end game damage is so high that you quickly get a full charge bar immediately after losing it......
Red Wolf scales with FOC, and procs every time you crit. However, it only hits melee targets. Builds fully utilizing Red Wolf are possible, although it is also equally possible to splash 1 point into other builds; I think this could easily be fixed by causing the damage to scale linearly - I don't think this would cause many early game problems for Red Wolf builds.
Another skill that falls into the 1 point wonder category would be Rampage, since the only thing that scales on Rampage is the % chance to proc on kill. It applies a non-stacking buff, and on Synergies with the higher monster count, you tend to have Rampage up more often than not (if you progress quickly enough, and with a decent killing build).