Toe can affect not only how the car drives, but also the driver's perception of how the car drives. If the alignment is perfect with the exception that the steering wheel is off-center when driving straight, 9 out of 10 drivers will perceive that as the car pulling to one side.

Benzs are not harder to align, but not every tech has experience with 'em. Because Mercedes uses an agressive caster angle, camber measurements vary greatly as the wheel turns off center. If the wheel is not pointing straight ahead, the camber measurement is meaningless.

Any part in the suspension or steering linkage can fail and render the suspension “un-alignable”. A tech should check for failing joints and bushings before attempting an alignment.

I'd take the car back and make 'em straighten it out.

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1989 300 SEL that mostly works, but needs TLC