Rebecca, as you say very, very time consuming. I've just tried it.
We can see a travellers 'reviews from other hosts', we can see 'reviews from 'his' guests', but we can't see reviews he has left as a guest for other hosts, without doing our own detective work.
But still this does not give a true idea of the guest because you might not have had an issue with the guest until after you have left your review only to find out that he has left a ghastly review full of lies. As in my case I recommended him and said he was welcome back. Once I saw what he wrote there is no way I would recommend him to other hosts, he is a lier and could ruin another host's reputation and even get a host's account suspended (I am on the verge of suspension). Sometimes a guest's bad review is not really about the place it's more about the fact that the guest took a disliking to the host and wants to get back at them for some strange reason...