Let me clarify a little. Everyone was saying that when they connect the Helix and DT via L6 that the topology switch goes out so you can't adjust the voicing. With firmware v1.0 I still have control of the switch and can change between I, II, II and IV. I am not controlling this from the Helix but I can control it manually unlike the latest firmware that renders the switch inoperable.
I tried setting the pre-amp and cab to none so that I was just using the power tube section but I didn't like the tone. Everything sounded muddy and it didn't mix well with the rest of the band.
Now that I am back to v1.0, I set my voicing to IV, gain to 0, bass/mid/treble and channel volume to 12 o'clock, just a touch of presence, and no reverb. I like the tones I get which is all that really matter, right?