a new kit on the md has the default of the compressor mix set to max. In addition the controls of the compressor mix are reverse of most the other controls, full counter-clockwise (0) is full wet and full clockwise(127) is completely dry.
Compression is occurring at the final mix because the total signal of all the tracks combined is too hot. Turn down the vol parameter of all sound to half to start then mix volumes from there. The default vol is at max. The effect of the level parameter becomes a boost above 100 or so and the distortion parameter can also influence gain staging a bit.
phase cancellation of two hits occurring at the same time
The default compressor settings are setup like a Limiter. My guess is they have it on by default so of you’re playing live or just creating a new kit and not paying a lot of attention you won’t accidentally blast your ears/speakers because you had something way louder than the previous kit. I’m not too sure why the wet/dry knob is reversed though.