If the band leader can't compensate for a slightly weaker signal from one of the instruments then why is he in charge of the sound? You set your sound on the HX stomp, he is then responsible for the level, if it needs more, he just needs to boost it. Sounds like he isn't changing any settings between different gigs which is worrying, every room is different!
Bassists tend to get the blame a lot for their volume, I've had guitarists who have too much bottom end, keyboard players who aren't used to full band situations so add in all the lows... it's always the bassists fault though!