The latency you are experiencing is probably because of the Microsoft GS Wavetable synth. It's a softsynth, and these usually have a certain amount of latency in responding to real-time MIDI commands. Of course, when a MIDI sequence plays, this is not noticeable...
I'm not sure if Voyetra Digital Orchestrator supports ASIO or WDM drivers, or can act as a VST or DX host. You could get better results if it does by using a VST or DX instrument and if your soundcard has decent ASIO or WDM drivers. You can also use
the DD-55 as a drum module -- send the MIDI commands out to it rather than to the softsynth.
To get the DD-55 sounds on the computer, you have to record them to as audio -- which you have to do at some point anyway if you want to mix it all to a CD in the end. You can record the MIDI data and use that until mixdown, and then arm a track and record the output of the drum box while it's playing back in response to the MIDI messages.
Either way, if you record the MIDI drum part in the sequencer and then record your guitar over it over it, everything should be fine. The inherent delay in the audio stream is compensated for, so as long as you don't monitor the input after it's been digitized and processed, there will be no delay to worry about.