Meh on Daltrey now. compare it to Who's Next and you'll see what I mean.
Stevie Nicks always sounded like a goat. a sexy goat, but a goat nevertheless. Rhianon. Sounds like a goat. don't get me wrong - that picture on the inside jacket of Rumours is fantastic, but I was amazed that the South Park episode on the boys sneaking over to Afghanistan had a goat appear for Stevie Nicks on her visit to the troops. The writers of South Park also think recognized she sounds like a goat. "Sara" is another goat song.
I have not heard Rod lately, so honestly can't say. I think the singers who do the worst as they age are the ones that both scream and try to sing. Springsteen is a good example. I love The Rising and Magic, but he just can't hit the notes he used to and makes it up on amplification. compare the vocals to say, Greetings or The River and you can hear the deterioration.