To add on to the good tips above, be patient
Good analog synth drum sounds seem to take a while. Classic analog drum machines, the engineers were working on those sounds for weeks...
One way to get more complexity is to separate the sound into a stick/click element, and a body element. You can add an oscillator's level knob to the mod matrix. Turn the level knob all the way down, then modulate that knob with one of the envelopes, to make it into an extra VCA for that oscillator. Or, if you are splitting the oscillators to each filter (with the filters routed in parallel), control the output volume for one or both filters with an envelope. That way you can have the stick decay quickly, and even have the body fade in if you want. The stick can be a short burst of noise, or an interesting alternative is a high pitched tone from an oscillator, it still sounds like a click, just different.
Couple other thoughts, the audio rate modulation opens up a lot of new percussion sounds. It often sounds good with using the mellow oscillator shapes, the triangle and sine waves, since it is adding upper harmonics through the AM or FM.
-The metalizer knob for the triangle wave does in fact add a metalic sound. Interesting sounds with envelope control.
-Hi hat sounds need some kind of hi-pass filter to make it thin and light sounding.
-Toms don't need much noise.
-Some kind of distortion on a kick sound can be good, albeit more industrial sounding.
-short delays from the flanger, with the cycle turned off, but the repeats turned up, could help get a tubey resonance. Sort of crude physical modeling. Turn the repeats off, and the mix to 50/50, and it is a comb filter, for a hollow, boxey sound.
The Synare line of 70's analog drum synths had some really nice sounds, for simple circuits (that could be replicated by the MxB). Joy Division, The Cure. There's a cool one they both use that sounds like the sound when you hit a spring reverb, I'd like to figure out.
