Okay, I took the TD-4 to just be the sound module, but it's the whole electronic kit. Electronic drums aren't my specialty.
Can you monitor the audio from the TD-4 while recording the MIDI, then convert the MIDI to audio with Drumcore after the fact? If not, or if you need the Drumcore sounds to get the performance you want, maybe someone with more MIDI/computer skills will come along to help reduce the latency.