I'm currently playing in two very different bands - the third (originals) band is on a semi-permanent hold at the moment, so I won't bother with that (different again) situation.
One band is a primarily function/wedding band, uses a fair few very high quality deps (drummer and guitard, very occasionally bassist when I can't make it) and never rehearses. It's well organised, the arrangement and key of the songs are set out from the start (a single reference version is circulated) and it works very well. There's a proper professional attitude taken to it all, and playing with a great dep really lifts everyone's game,and is a unique learning experience.
The second band is a Rawk band with some old friends which is having its first gig this weekend, so we've had maybe six or eight rehearsals as much as a social night out as anything, and that works very well, too. We expect to gig maybe once a month, and once we're gigging, I can see another rehearsal once a month to introduce new songs - we tend to rework stuff to suit ourselves, which is again a different, enjoyable experience.
I think the OP's issue isn't specifically with the methodology of the setup, but that he feels out of his depth with it, which is understandable given the pressure and time constraints he's under.