Allow me to play Devil's Advocate here, although I do broadly agree with you.
Certainly it's much more precise to know exactly what note you're playing and when, especially if the band isn't a 'jam band' (I don't use that term derisively - a lot of deps I do take a less structured approach and that has its own strength). My trepidation in using a score, other than the time required to write it, is that not everyone is a reader; in fact at least one of the people I would consider using as a dep isn't. Great player, just not something they do. Plus, you'd have to make sure your scoring was dead accurate to the band you're playing with.
Where the lyrics/chords approach has merit is for being able to follow along with the vocal line to get a sense of where you are. This is typically how I lay out my own reference material, with the occasional passage of notation if needed. That said, it still requires someone to know how a song goes, roughly - and your example is a good one illustrating the lack of info such an approach yields (although I do often write some instructive text for myself). I'm hoping I can secure my deps far enough in advance that they'll be able to go over all the tunes beforehand, but I suppose that doesn't account for the instances where I might be hit by a bus the day of a wedding and need someone that day who doesn't know all the songs.
I suppose the best approach would be a combination of all three styles, wouldn't it? Chords on top, notation below it, lyrics below that, with some structural notes written as and when needed. It would take a long time to make and get right, but maybe I just need to get on with it to give my hypothetical deps the best chance of nailing it.