But Maddock intercepted to complete his treble before Barkley finished off a fine move to put Bath three points ahead of Wasps with one game remaining.
Bath centre Tom Cheeseman is one possibility after a fine season with the Guinness Premiership side, but he faces stiff competition from several of his Wales Under-21s team-mates.
Evans continued his fine performance with two more successful penalties after the beak, with Vesty replying for Bath in between, as the second half began to get niggly with a number of flare-ups.
Wasps were good value for their early lead but when Bath finally secured some possession their superb off-loading and incisive running brought about two fine tries for Maddock.