I noticed that the first rank of "Fitness" provides an extremely powerful upgrade:
However, the next level provides a much smaller upgrade, but displays a "green bar" showing what is actually being improved:
So does this mean the first rank (for a measly 1 point) really give me 15% health, shield and melee damage bonus, while the second rank (2 points) only gives 10% more health and shield? Is this how all skills work?