Alex Just to repeat what's already been said but...
As you may know the drive on the MXR automatically engages the modern function so you're getting a more modern scoop to the tone. The W&C PPB gives a useful boost and it'll defo bump you in the live mix. I used one in conjunction with a ODB-3 with good effect!
Does your bass core tone have a scoop to it and maybe your needing to adjust where you sit in the mix, push the mids more to popke out between the guitars?
I like the MXR Bass OD but it does add some of that modern sound on the clean blend knob - Ashdown Lomenzo Hyperdrive or the Nate Mendel might be worth a look (the demo's at least) to see if your needing a specfic frequency boosted or something with a clean blend to keep your core tone thick and present
Perhaps a eq pedal would allow you to boost the frequencies in conjunction with your current drive?
Would the guitarist be willing to look at the bands sound as a whole unit and tailor their tone so you have a good big wall of sound? I suspect you'll have to fit in with their sound.
Half the fun is finding your place in the mix and maybe your next practice you should go with the mindset of doing that and not concenbtrating on the actual rehearsal? for maybe the last 30 minutes get the band to play the same tune a cple of times, record each take on your phone if you can, make adjustments to your EQ (and write them down), record, adjust and repeat. Get the guys in the band involved and get their opinion too cause once you all have your place in the mix you'll be a better sounding band. Listen back at home the following day, maybe get the lads frok the band round too to hear the differences. It's more productive than getting frustrated that you've wasted money and time on rehearsal and you will sound better as a unit, make recording easier in the future etc etc.
I look forward to hearing how you get on!!