Frankly, I think Jobs need to have more than just 5 abilities tied to them. They should also alter about half of the traits a given class has. This would also allow classes to branch into multiple jobs with fewer conflicts, as well as giving jobs a significantly different feel compared to the base class.

For example, give Gladiator a decent mix of offensive and defensive traits. When they change to Paladin, the offensive traits would convert to more defensive/tank utility traits. And down the road if Gladiator gets a dps job tied to it, the defensive traits could convert to more offensive/dps utility traits.