It doesn’t matter how the complexity of the workers’ duties compares to those of other workers. For Barnes’s argument, it only matters if they’re too complex for inexperienced workers.

Barnes’s claim is simply that the employees’ salaries should be reduced because they’re too high for inexperienced employees, and that the complexity of their tasks should be reduced because they're too complex for inexperienced employees; it doesn’t matter why the current salaries are high. Even if the salaries were not causally connected to the kind of tasks they're assigned, the author could still argue that their tasks are more complex than what is given to new employees and that their salaries are too high for what is given to new employees.

This must be true in order for the conclusion to follow. If these two new workers were experienced, then their duties wouldn’t necessarily be too complex for them.

Barnes’s personal circumstances are irrelevant to what’s logically required for his conclusion. The author's own salary is irrelevant to the argument she makes about the two newest employees.

It doesn’t matter how the employees’ salaries compare to those of workers at other companies. For Barnes’s argument, it only matters that their salaries are higher than what is proper for new employees assigned simple tasks.