The problem is most likely to do with the input attenuation. The waveform in the OP looks like the digital converter is clipping. I recommend you attenuate the microphone input to fix this. Start at the highest level of attenuation (-18dB) and then decrease until clipping starts, then reduce back one level.
I think hard panning as opposed to 50%L/R is just personal preference - nothing to do with phase cancellation.
Obviously with hard L/R you will get a wider stereo sound-stage - I think it just depends on what you want in the mix. You can also try and introduce some chorus and delay to give you even more depth to the sound.