UPDATE
Not sure if my ears were just tired, or if this really made a difference, but I upgraded my firmware and it did seem to help. To me, the 2.0 B1 Four update seems to be an improvement.
Ear fatigue can happen pretty quickly when trying out a new multi-effect., even within the same Zoom family. Sometimes I like to set the tuner to Bypass mode so that I can quickly toggle ALL the effects off in a single pedal push, just to hear if I'm too heavy on EQ or other tonal changes inside the patch.
Glad to hear the B1 Four is starting to work out better for you after the update. Also agreed on the LPF/HPF function - a well thought out choice to be offered in a bass multi-effect unit.