No engine "needs" a fluid dampener. And the only difference between an internally balanced engine and an externally balanced one is the proper counterbalance weights on the balancer and rear crank flange.
The "balancer" is actually a harmonic dampener. Every object has a natural resonant frequency. And excited in a certain fashion, those vibrations manifest themselves as harmonics- integer multiples of the resonant frequency of the object. And like the singer breaking the glass, those harmonics can compound until physical damage occurs. Thus the damper.
The "balancer" on your engine may or may not be participating in the dynamic balance of your rotating assembly, but all of them exist to dampen the harmonics that might otherwise lead to significant damage.