Not at all unrealistic. I could never be in a band with someone like your guitarist. It would drive.me.bonkers. Do the singer and guitarist want to gig? If so, Mr G needs to get his sheeite together unless he wants you to look like an under-rehearsed shambles. If they don't want to gig, you're wasting your time. A proper sit-down meeting is required for all of you, so you can work out what everyone actually wants from the band, before you go to all the effort of getting a new drummist on board.