A sneaky system design quirk may contribute to D&D campaigns fizzling out before they reach high level.
Examining the Gunslinger's Misfire mechanic as a cautionary tale for importing character options from other games. Why to never base a class on a "critical fumble" mechanic.
Eberron's new Changeling is the first class that can start with an 18 ability score at level 1. Although this "power creep" doesn't mean the class is unbalanced, the answer to rebalancing the race within the existing design paradigm may lay within cut content.