Is the Dunable handling the low tuning? I'll assume so.
You need sustain more than drive. When testing, play slow and ring notes out. Compression is likely a key factor with this.
When getting that low, the scooped nature of darkglass gear might not help with clarity. I'd try backing off the dirt from the amp head but hitting it with some pedals that don't mid scoop, after the compressor. Avoid big muffs.
Stacking 2 drive pedals at lower dirt settings will likely work better than one pedal.
The main issue will be pedals that don't cut your low end.
Another option is using an eq pedal to smash more mids into your amps on board drive. Be bold with the eq!