Might I suggest that you EQ your output differently for stage mix. Remove a lot of the low end bass and brighten the mix, this will allow you to hear the drums easier. You can't stay in rhythm if you can't hear it. Also what someone else recommended about speaker placement, use hotspots or good floor monitors. Also, practice, practice, practice.... Drummers are use to controlling time, and with an arranger or drum machine, they can't unless your arranger has a feature to allow you to tap in time (Tap Tempo) and assign to a pedal, allow the percussionist to control the time this way.