[BluE_MeaniE]

Well, I do think it's hard to be a good guitarist. But it really depends on who you're playing to. For many audiences, all you need is five notes, the minor pentatonic scale. Just jam on that, people will go nuts.
Now, other audience members, maybe who know more about music, or have a different view on it (not that it's bad the other way) just sometimes need other things to really enjoy it.
And yes, drummers need to be able to at least keep the beat, if they can't do that, then it's very difficult.
Hey, what do you call a drummer who broke up with his girlfriend? Homeless. Yuk yuk yuk.
Okay, I'm sorry, that was a terrible joke, but it's the only one I know.

But as you've said, your singer had a unique voice that was entertaining to listen to. That's can be just so good, and successful for playing live.