Filters with just reactive elements are reflective in the rejection band. You can make a diplexer which diverts the frequencies in the notch to a dummy load.
Alternately, you can include the notch in the transistor output network. Some of the high efficiency amplifier topologies use this method to square up the voltage waveforms while allowing a sinusoidal current waveform.
In general, a circulator is a good addition if you are in a high signal environment. It keeps RF power from near by transmitters coming back down the antenna-transmission line and causing IMD in your amplifier.