As for him 'overusing' his talent, well I can only say I disagree, mostly. I realise there is this myth-making tendency given his early death and all, but I'd like to think that for myself at least, it's not really the reason I listen to his music. Especially since the impression I always had was his death was an accident pure and simple. Shit happens, but I don't view him through some sort of tortured-genius prism.
Of course he should (hopefully would) have grown as a songwriter, but it's a moot point now, innit?
This is not Celine Dion we are talking about. I am not a fan of vocal technique for its own sake either, but honestly I've never felt that particular vibe in Jeff Buckley's music.
Must admit I know naught about father Tim. Any particular record I should start with?