Band Chemistry

Is there a particular “rule” to follow when “putting together” your band? I always find that the band chemistry is somewhat mediocre (50) even with a full ensemble (either with just bass, drums and guitar, OR with the aforementioned plus sax and keyboaard).

I don’t know why it never goes much higher than this…

Here’s what I have

Bass: Optimistic, Photogenic
Drums: Businesslike, Articulate
Guitar: Peacemaker, Optimistic
Keyboard: Ambitious, Businesslike
Saxophone: Ambitious, Socialiser, Energetic

Seems like a pretty like-minded bunch, yet I can guarantee two of them won’t like each other (usually the bass and guitar players start to get annoyed with each other).

I’m not sure what I can do to increase band harmony? Should I really be adding disruptive and egotistical members into the band? I’ve never bothered because I thought it would disrupt the band harmony…

Also, is there a way for vocals to get ANY better? Even with constant practice, vocals don’t seem to improve all that much…