You can interpret the difference between OU/BL in several ways. Really it doesn't matter since they're both the same tier really.
And honestly I don't care what Smogon says, there IS a NU tier and you should really put one on here. If you have to, use Smogon's ADV pagwe to determine the tiers.
Because seriously leaving out a full tier is nonsense. Again I don't care what Smogon says (after all, they're the morons that say Wobbuffet is OU :/)
BTW Ooka this is off-topic but were you by any chance on Netbattle today? Soembody battled me and went "yeah I knew that team looked familiar" and I'm like O_O
Back to tier listings, if there's a tier to get rid of, it's BL. It's honestly a really useless tier. We need NU or this tier list isn't really as good because I used to play NU a lot. I honestly have no clue about this gen's tier thing but I'd like to know. So I say bring back NU! Bring down Smogon!
EDIT: Dugtrio is OU. I've seen plenty on Shoddy :(