Big Muff Pi = NOT an overdrive. Plus, it has a variable mid-scoop notch which can contribute to not being heard in the mix.
Fuzz is a difficult pedal to incorporate in a band, and the Big Muff Pi is notorious for needing "sonic space" to be heard. Other fuzz pedals can stand out better, but the thicker the mix, the more trouble you'll have. Same goes for anything above mild overdrive.
On a side note - I think that Behringer pedal is a copy of the Boss ODB-3. Not one of my favorite overdrives (in fact, it's on my "hate" list), but hey, it floats some bassists' boats, and it floats yours, too.
