If it's top 50 then no, certainly not a bug (weird people put up weird decks), if it's level 3, then the ai just got very unlucky.
(I wonder how they'd get to the top 50 in the first place, (With no damagers, creatures, etc) Also, I fought one TOP 50 that looked liked this: (http://imageplay.net/view/m7Gbd130524/Capture1) (http://imageplay.net/view/m7Gbd130525/Capture)I didn't hack (Just incase, not saying anything here), but they're weird... AND I had this really weird thing too. He was using Death mark, but the weird thing is , I got _3_ pulverizers in a row. (Spin) Either it was luck, or the spin only chose that card because he had that card (besides pillars)