I'm afraid there is no way to get better results.
The issue with YM2612 drums is, that they are PCM based. Due to how this works, VGMs only contain the streamed WAVE data for them.
vgm2mid converts all the separate PCM samples (like "samples in a WAVE file", not "sound samples") into MIDI notes (with a small filter though), so with some luck you can find a few notes that are only used by certain samples and filter the rest out.
The only other possibility would be to omit them entirely.
If you want songs from the Sonic series, you can alternatively use
smps2mid.