I used the Yokohamas last year and because of the somewhat unfortunate weather (lots of damp running) got a fairly good feel for what they could do. Not bad.
Unfortunately, wet running can be so varied, it is impossible to have thee best tire for the conditions.
Apparantly the Hoosier dirt stocker is the best for pouring rain and standing water (if there is anything that comes close to working). However, I have heard good things about a full tread Kuhmo and I used to use a TOYO Proxes for the rain, which was a good tire also. These tires may last longer in drying conditions.
Make certain you have something!